diff --git a/packages/babel-generator/test/fixtures/flow/declare-field/input.js b/packages/babel-generator/test/fixtures/flow/declare-field/input.js
new file mode 100644
index 0000000000..f0db8dde17
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/flow/declare-field/input.js
@@ -0,0 +1,4 @@
+class A {
+  declare x
+  declare static y
+}
diff --git a/packages/babel-generator/test/fixtures/flow/declare-field/options.json b/packages/babel-generator/test/fixtures/flow/declare-field/options.json
new file mode 100644
index 0000000000..65c79d81c7
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/flow/declare-field/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["flow", "classProperties"]
+}
diff --git a/packages/babel-generator/test/fixtures/flow/declare-field/output.js b/packages/babel-generator/test/fixtures/flow/declare-field/output.js
new file mode 100644
index 0000000000..7d405964d2
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/flow/declare-field/output.js
@@ -0,0 +1,4 @@
+class A {
+  declare x;
+  declare static y;
+}
\ No newline at end of file
diff --git a/packages/babel-parser/src/parser/statement.js b/packages/babel-parser/src/parser/statement.js
index 7c435b4aa1..794667bb35 100644
--- a/packages/babel-parser/src/parser/statement.js
+++ b/packages/babel-parser/src/parser/statement.js
@@ -1240,50 +1240,59 @@ export default class StatementParser extends ExpressionParser {
     return this.finishNode(classBody, "ClassBody");
   }
 
+  // returns true if the current identifier is a method/field name,
+  // false if it is a modifier
+  parseClassMemberFromModifier(
+    classBody: N.ClassBody,
+    member: N.ClassMember,
+  ): boolean {
+    const containsEsc = this.state.containsEsc;
+    const key = this.parseIdentifier(true); // eats the modifier
+
+    if (this.isClassMethod()) {
+      const method: N.ClassMethod = (member: any);
+
+      // a method named like the modifier
+      method.kind = "method";
+      method.computed = false;
+      method.key = key;
+      method.static = false;
+      this.pushClassMethod(
+        classBody,
+        method,
+        false,
+        false,
+        /* isConstructor */ false,
+        false,
+      );
+      return true;
+    } else if (this.isClassProperty()) {
+      const prop: N.ClassProperty = (member: any);
+
+      // a property named like the modifier
+      prop.computed = false;
+      prop.key = key;
+      prop.static = false;
+      classBody.body.push(this.parseClassProperty(prop));
+      return true;
+    } else if (containsEsc) {
+      throw this.unexpected();
+    }
+
+    return false;
+  }
+
   parseClassMember(
     classBody: N.ClassBody,
     member: N.ClassMember,
     state: { hadConstructor: boolean },
     constructorAllowsSuper: boolean,
   ): void {
-    let isStatic = false;
-    const containsEsc = this.state.containsEsc;
+    const isStatic = this.isContextual("static");
 
-    if (this.match(tt.name) && this.state.value === "static") {
-      const key = this.parseIdentifier(true); // eats 'static'
-
-      if (this.isClassMethod()) {
-        const method: N.ClassMethod = (member: any);
-
-        // a method named 'static'
-        method.kind = "method";
-        method.computed = false;
-        method.key = key;
-        method.static = false;
-        this.pushClassMethod(
-          classBody,
-          method,
-          false,
-          false,
-          /* isConstructor */ false,
-          false,
-        );
-        return;
-      } else if (this.isClassProperty()) {
-        const prop: N.ClassProperty = (member: any);
-
-        // a property named 'static'
-        prop.computed = false;
-        prop.key = key;
-        prop.static = false;
-        classBody.body.push(this.parseClassProperty(prop));
-        return;
-      } else if (containsEsc) {
-        throw this.unexpected();
-      }
-
-      // otherwise something static
-      isStatic = true;
+    if (isStatic && this.parseClassMemberFromModifier(classBody, member)) {
+      // a class element named 'static'
+      return;
     }
 
     this.parseClassMemberWithIsStatic(
diff --git a/packages/babel-parser/src/plugins/flow.js b/packages/babel-parser/src/plugins/flow.js
index 2f32adcb99..e445df729f 100644
--- a/packages/babel-parser/src/plugins/flow.js
+++ b/packages/babel-parser/src/plugins/flow.js
@@ -51,6 +51,10 @@ const FlowErrors = Object.freeze({
   AmbiguousDeclareModuleKind:
     "Found both `declare module.exports` and `declare export` in the same module. Modules can only have 1 since they are either an ES module or they are a CommonJS module",
   AssignReservedType: "Cannot overwrite reserved type %0",
+  DeclareClassElement:
+    "The `declare` modifier can only appear on class fields.",
+  DeclareClassFieldInitializer:
+    "Initializers are not allowed in fields with the `declare` modifier.",
   DuplicateDeclareModuleExports: "Duplicate `declare module.exports` statement",
   EnumBooleanMemberNotInitialized:
     "Boolean enum members need to be initialized. Use either `%0 = true,` or `%0 = false,` in enum `%1`.",
@@ -2085,6 +2089,39 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       }
     }
 
+    parseClassMember(
+      classBody: N.ClassBody,
+      member: any,
+      state: { hadConstructor: boolean },
+      constructorAllowsSuper: boolean,
+    ): void {
+      const pos = this.state.start;
+      if (this.isContextual("declare")) {
+        if (this.parseClassMemberFromModifier(classBody, member)) {
+          // 'declare' is a class element name
+          return;
+        }
+
+        member.declare = true;
+      }
+
+      super.parseClassMember(classBody, member, state, constructorAllowsSuper);
+
+      if (member.declare) {
+        if (
+          member.type !== "ClassProperty" &&
+          member.type !== "ClassPrivateProperty"
+        ) {
+          this.raise(pos, FlowErrors.DeclareClassElement);
+        } else if (member.value) {
+          this.raise(
+            member.value.start,
+            FlowErrors.DeclareClassFieldInitializer,
+          );
+        }
+      }
+    }
+
     // ensure that inside flow types, we bypass the jsx parser plugin
     getTokenFromCode(code: number): void {
       const next = this.input.charCodeAt(this.state.pos + 1);
diff --git a/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field-initializer/input.js b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field-initializer/input.js
new file mode 100644
index 0000000000..7f38766c9f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field-initializer/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare #foo = 2
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field-initializer/output.json b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field-initializer/output.json
new file mode 100644
index 0000000000..d8b704a351
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field-initializer/output.json
@@ -0,0 +1,158 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 30,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Initializers are not allowed in fields with the `declare` modifier. (2:17)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 30,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 30,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 30,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 28,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 18
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 20,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 14
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 21,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 14
+                    },
+                    "identifierName": "foo"
+                  },
+                  "name": "foo"
+                }
+              },
+              "variance": null,
+              "value": {
+                "type": "NumericLiteral",
+                "start": 27,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 17
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 18
+                  }
+                },
+                "extra": {
+                  "rawValue": 2,
+                  "raw": "2"
+                },
+                "value": 2
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field/input.js b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field/input.js
new file mode 100644
index 0000000000..bc3b7c37d3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare #foo
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field/output.json b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field/output.json
new file mode 100644
index 0000000000..0b28665941
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-field/output.json
@@ -0,0 +1,136 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 26,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 26,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 26,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 26,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start": 12,
+              "end": 24,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 14
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 20,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 14
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 21,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 14
+                    },
+                    "identifierName": "foo"
+                  },
+                  "name": "foo"
+                }
+              },
+              "variance": null,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/input.js b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/input.js
new file mode 100644
index 0000000000..edfd99fe60
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare #foo() {}
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/options.json b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/options.json
new file mode 100644
index 0000000000..3bec5045a3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/options.json
@@ -0,0 +1,8 @@
+{
+  "sourceType": "module",
+  "plugins": [
+    "flow",
+    "classPrivateProperties",
+    "classPrivateMethods"
+  ]
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/output.json b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/output.json
new file mode 100644
index 0000000000..14ff0e5a49
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-private-property/declare-method/output.json
@@ -0,0 +1,159 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 31,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: The `declare` modifier can only appear on class fields. (2:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 31,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 31,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 31,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassPrivateMethod",
+              "start": 12,
+              "end": 29,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 19
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start": 20,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 14
+                  }
+                },
+                "id": {
+                  "type": "Identifier",
+                  "start": 21,
+                  "end": 24,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 14
+                    },
+                    "identifierName": "foo"
+                  },
+                  "name": "foo"
+                }
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 27,
+                "end": 29,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 17
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 19
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/input.js
new file mode 100644
index 0000000000..6075fd0137
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/input.js
@@ -0,0 +1,3 @@
+class A {
+  @dec declare foo
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/options.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/options.json
new file mode 100644
index 0000000000..71e345f908
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/options.json
@@ -0,0 +1,8 @@
+{
+  "sourceType": "module",
+  "plugins": [
+    "flow",
+    "classProperties",
+    ["decorators", { "decoratorsBeforeExport": false }]
+  ]
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/output.json
new file mode 100644
index 0000000000..8750916dc0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-after-decorators/output.json
@@ -0,0 +1,156 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 30,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 30,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 30,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 30,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 28,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 18
+                }
+              },
+              "decorators": [
+                {
+                  "type": "Decorator",
+                  "start": 12,
+                  "end": 16,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 2
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 6
+                    }
+                  },
+                  "expression": {
+                    "type": "Identifier",
+                    "start": 13,
+                    "end": 16,
+                    "loc": {
+                      "start": {
+                        "line": 2,
+                        "column": 3
+                      },
+                      "end": {
+                        "line": 2,
+                        "column": 6
+                      },
+                      "identifierName": "dec"
+                    },
+                    "name": "dec"
+                  }
+                }
+              ],
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 25,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 15
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 18
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "computed": false,
+              "variance": null,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-before-decorators/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-before-decorators/input.js
new file mode 100644
index 0000000000..069fd4fb33
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-before-decorators/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare @dec foo
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-before-decorators/options.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-before-decorators/options.json
new file mode 100644
index 0000000000..43ca4a74f8
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-before-decorators/options.json
@@ -0,0 +1,9 @@
+{
+  "sourceType": "module",
+  "plugins": [
+    "flow",
+    "classProperties",
+    ["decorators", { "decoratorsBeforeExport": false }]
+  ],
+  "throws": "Unexpected token (2:10)"
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-constructor/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-constructor/input.js
new file mode 100644
index 0000000000..ad173f3e1a
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-constructor/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare constructor() {}
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-constructor/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-constructor/output.json
new file mode 100644
index 0000000000..af984299b9
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-constructor/output.json
@@ -0,0 +1,145 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: The `declare` modifier can only appear on class fields. (2:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 38,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 38,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start": 12,
+              "end": 36,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 26
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 20,
+                "end": 31,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 21
+                  },
+                  "identifierName": "constructor"
+                },
+                "name": "constructor"
+              },
+              "computed": false,
+              "kind": "constructor",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 34,
+                "end": 36,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 24
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 26
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-computed/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-computed/input.js
new file mode 100644
index 0000000000..14a7727471
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-computed/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare [foo]
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-computed/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-computed/output.json
new file mode 100644
index 0000000000..722c81c068
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-computed/output.json
@@ -0,0 +1,122 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 27,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 27,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 27,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 27,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 25,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 15
+                }
+              },
+              "declare": true,
+              "static": false,
+              "computed": true,
+              "key": {
+                "type": "Identifier",
+                "start": 21,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 11
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 14
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "variance": null,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-initializer/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-initializer/input.js
new file mode 100644
index 0000000000..7d9387f547
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-initializer/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare foo = 2
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-initializer/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-initializer/output.json
new file mode 100644
index 0000000000..0de5fd4795
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-initializer/output.json
@@ -0,0 +1,144 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 29,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: Initializers are not allowed in fields with the `declare` modifier. (2:16)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 29,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 29,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 29,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 27,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 17
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 20,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "computed": false,
+              "variance": null,
+              "value": {
+                "type": "NumericLiteral",
+                "start": 26,
+                "end": 27,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 16
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 17
+                  }
+                },
+                "extra": {
+                  "rawValue": 2,
+                  "raw": "2"
+                },
+                "value": 2
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-named-static/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-named-static/input.js
new file mode 100644
index 0000000000..c746a01c76
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-named-static/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare static
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-named-static/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-named-static/output.json
new file mode 100644
index 0000000000..bcba26999c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-named-static/output.json
@@ -0,0 +1,121 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 28,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 28,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 28,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 28,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 26,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 16
+                }
+              },
+              "declare": true,
+              "computed": false,
+              "key": {
+                "type": "Identifier",
+                "start": 20,
+                "end": 26,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 16
+                  },
+                  "identifierName": "static"
+                },
+                "name": "static"
+              },
+              "static": false,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-with-type/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-with-type/input.js
new file mode 100644
index 0000000000..80b1bbb04e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-with-type/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare foo: string
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-with-type/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-with-type/output.json
new file mode 100644
index 0000000000..03de79fdb3
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field-with-type/output.json
@@ -0,0 +1,152 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 33,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 33,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 33,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 33,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 31,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 21
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 20,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "computed": false,
+              "variance": null,
+              "typeAnnotation": {
+                "type": "TypeAnnotation",
+                "start": 23,
+                "end": 31,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 21
+                  }
+                },
+                "typeAnnotation": {
+                  "type": "StringTypeAnnotation",
+                  "start": 25,
+                  "end": 31,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 15
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 21
+                    }
+                  }
+                }
+              },
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field/input.js
new file mode 100644
index 0000000000..9e7ac1ffb0
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare foo
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-field/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field/output.json
new file mode 100644
index 0000000000..ea95861352
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-field/output.json
@@ -0,0 +1,122 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 25,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 25,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 25,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 25,
+          "loc": {
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+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 23,
+              "loc": {
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+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 13
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 20,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "computed": false,
+              "variance": null,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-method/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-method/input.js
new file mode 100644
index 0000000000..0e539a84a2
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-method/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare foo() {}
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-method/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-method/output.json
new file mode 100644
index 0000000000..863648b54e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-method/output.json
@@ -0,0 +1,145 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 30,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "errors": [
+    "SyntaxError: The `declare` modifier can only appear on class fields. (2:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 30,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 30,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 30,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start": 12,
+              "end": 28,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 18
+                }
+              },
+              "declare": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start": 20,
+                "end": 23,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 10
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 13
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 26,
+                "end": 28,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 16
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 18
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-static-field/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/declare-static-field/input.js
new file mode 100644
index 0000000000..00d59b89a1
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-static-field/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare static foo
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/declare-static-field/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/declare-static-field/output.json
new file mode 100644
index 0000000000..d9c35eafd5
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/declare-static-field/output.json
@@ -0,0 +1,122 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 32,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 32,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 32,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 32,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 30,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 20
+                }
+              },
+              "declare": true,
+              "static": true,
+              "key": {
+                "type": "Identifier",
+                "start": 27,
+                "end": 30,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 17
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 20
+                  },
+                  "identifierName": "foo"
+                },
+                "name": "foo"
+              },
+              "computed": false,
+              "variance": null,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare-with-type/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare-with-type/input.js
new file mode 100644
index 0000000000..596b91c311
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare-with-type/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare: string
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare-with-type/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare-with-type/output.json
new file mode 100644
index 0000000000..183b79323c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare-with-type/output.json
@@ -0,0 +1,150 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 29,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 29,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 29,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 29,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 27,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 17
+                }
+              },
+              "computed": false,
+              "key": {
+                "type": "Identifier",
+                "start": 12,
+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "identifierName": "declare"
+                },
+                "name": "declare"
+              },
+              "static": false,
+              "typeAnnotation": {
+                "type": "TypeAnnotation",
+                "start": 19,
+                "end": 27,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 17
+                  }
+                },
+                "typeAnnotation": {
+                  "type": "StringTypeAnnotation",
+                  "start": 21,
+                  "end": 27,
+                  "loc": {
+                    "start": {
+                      "line": 2,
+                      "column": 11
+                    },
+                    "end": {
+                      "line": 2,
+                      "column": 17
+                    }
+                  }
+                }
+              },
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare/input.js
new file mode 100644
index 0000000000..4d078b4c0c
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare/output.json
new file mode 100644
index 0000000000..87652a453f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/field-named-declare/output.json
@@ -0,0 +1,120 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 21,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 21,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 21,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 21,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 19,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 9
+                }
+              },
+              "computed": false,
+              "key": {
+                "type": "Identifier",
+                "start": 12,
+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "identifierName": "declare"
+                },
+                "name": "declare"
+              },
+              "static": false,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/method-named-declare/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/method-named-declare/input.js
new file mode 100644
index 0000000000..a1c623ac12
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/method-named-declare/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare() {}
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/method-named-declare/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/method-named-declare/output.json
new file mode 100644
index 0000000000..e11d3c6e16
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/method-named-declare/output.json
@@ -0,0 +1,141 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 26,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 26,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 26,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 26,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start": 12,
+              "end": 24,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 14
+                }
+              },
+              "kind": "method",
+              "computed": false,
+              "key": {
+                "type": "Identifier",
+                "start": 12,
+                "end": 19,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 2
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "identifierName": "declare"
+                },
+                "name": "declare"
+              },
+              "static": false,
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start": 22,
+                "end": 24,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 12
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 14
+                  }
+                },
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/options.json b/packages/babel-parser/test/fixtures/flow/class-properties/options.json
new file mode 100644
index 0000000000..f7dcfe201b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/options.json
@@ -0,0 +1,4 @@
+{
+  "sourceType": "module",
+  "plugins": ["flow", "classProperties"]
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/static-declare-field/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/static-declare-field/input.js
new file mode 100644
index 0000000000..e7eae9b78e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/static-declare-field/input.js
@@ -0,0 +1,3 @@
+class A {
+  static declare foo
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/static-declare-field/options.json b/packages/babel-parser/test/fixtures/flow/class-properties/static-declare-field/options.json
new file mode 100644
index 0000000000..43a82ec8a1
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/static-declare-field/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token (2:17)"
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/static-field-named-declare/input.js b/packages/babel-parser/test/fixtures/flow/class-properties/static-field-named-declare/input.js
new file mode 100644
index 0000000000..79644eb64f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/static-field-named-declare/input.js
@@ -0,0 +1,3 @@
+class A {
+  static declare
+}
diff --git a/packages/babel-parser/test/fixtures/flow/class-properties/static-field-named-declare/output.json b/packages/babel-parser/test/fixtures/flow/class-properties/static-field-named-declare/output.json
new file mode 100644
index 0000000000..5cbe8625f5
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/flow/class-properties/static-field-named-declare/output.json
@@ -0,0 +1,121 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 28,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 3,
+      "column": 1
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 28,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 3,
+        "column": 1
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start": 0,
+        "end": 28,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 3,
+            "column": 1
+          }
+        },
+        "id": {
+          "type": "Identifier",
+          "start": 6,
+          "end": 7,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            },
+            "identifierName": "A"
+          },
+          "name": "A"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start": 8,
+          "end": 28,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 8
+            },
+            "end": {
+              "line": 3,
+              "column": 1
+            }
+          },
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start": 12,
+              "end": 26,
+              "loc": {
+                "start": {
+                  "line": 2,
+                  "column": 2
+                },
+                "end": {
+                  "line": 2,
+                  "column": 16
+                }
+              },
+              "static": true,
+              "key": {
+                "type": "Identifier",
+                "start": 19,
+                "end": 26,
+                "loc": {
+                  "start": {
+                    "line": 2,
+                    "column": 9
+                  },
+                  "end": {
+                    "line": 2,
+                    "column": 16
+                  },
+                  "identifierName": "declare"
+                },
+                "name": "declare"
+              },
+              "computed": false,
+              "variance": null,
+              "value": null
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-flow-strip-types/src/index.js b/packages/babel-plugin-transform-flow-strip-types/src/index.js
index bf4e5acaff..7779fd7523 100644
--- a/packages/babel-plugin-transform-flow-strip-types/src/index.js
+++ b/packages/babel-plugin-transform-flow-strip-types/src/index.js
@@ -2,13 +2,15 @@ import { declare } from "@babel/helper-plugin-utils";
 import syntaxFlow from "@babel/plugin-syntax-flow";
 import { types as t } from "@babel/core";
 
-export default declare(api => {
+export default declare((api, opts) => {
   api.assertVersion(7);
 
   const FLOW_DIRECTIVE = /(@flow(\s+(strict(-local)?|weak))?|@noflow)/;
 
   let skipStrip = false;
 
+  const { requireDirective = false, allowDeclareFields = false } = opts;
+
   return {
     name: "transform-flow-strip-types",
     inherits: syntaxFlow,
@@ -20,7 +22,6 @@ export default declare(api => {
           file: {
             ast: { comments },
           },
-          opts,
         },
       ) {
         skipStrip = false;
@@ -42,7 +43,7 @@ export default declare(api => {
           }
         }
 
-        if (!directiveFound && opts.requireDirective) {
+        if (!directiveFound && requireDirective) {
           skipStrip = true;
         }
       },
@@ -74,13 +75,6 @@ export default declare(api => {
         path.remove();
       },
 
-      ClassProperty(path) {
-        if (skipStrip) return;
-        path.node.variance = null;
-        path.node.typeAnnotation = null;
-        if (!path.node.value) path.remove();
-      },
-
       ClassPrivateProperty(path) {
         if (skipStrip) return;
         path.node.typeAnnotation = null;
@@ -94,8 +88,25 @@ export default declare(api => {
         // would transform the class before we reached the class property.
         path.get("body.body").forEach(child => {
           if (child.isClassProperty()) {
-            child.node.typeAnnotation = null;
-            if (!child.node.value) child.remove();
+            const { node } = child;
+
+            if (!allowDeclareFields && node.declare) {
+              throw child.buildCodeFrameError(
+                `The 'declare' modifier is only allowed when the ` +
+                  `'allowDeclareFields' option of ` +
+                  `@babel/plugin-transform-flow-strip-types or ` +
+                  `@babel/preset-flow is enabled.`,
+              );
+            }
+
+            if (node.declare) {
+              child.remove();
+            } else if (!allowDeclareFields && !node.value && !node.decorators) {
+              child.remove();
+            } else {
+              node.variance = null;
+              node.typeAnnotation = null;
+            }
           }
         });
       },
diff --git a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare-not-enabled/input.js b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare-not-enabled/input.js
new file mode 100644
index 0000000000..3cb9d54665
--- /dev/null
+++ b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare-not-enabled/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare x;
+}
diff --git a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare-not-enabled/options.json b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare-not-enabled/options.json
new file mode 100644
index 0000000000..73835049c4
--- /dev/null
+++ b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare-not-enabled/options.json
@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    "transform-flow-strip-types",
+    "syntax-class-properties"
+  ],
+  "throws": "The 'declare' modifier is only allowed when the 'allowDeclareFields' option of @babel/plugin-transform-flow-strip-types or @babel/preset-flow is enabled."
+}
diff --git a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/input.js b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/input.js
new file mode 100644
index 0000000000..7ab37b71fb
--- /dev/null
+++ b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/input.js
@@ -0,0 +1,3 @@
+class A {
+  declare x;
+}
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/options.json b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/options.json
new file mode 100644
index 0000000000..f5bedcb81a
--- /dev/null
+++ b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/options.json
@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    ["transform-flow-strip-types", { "allowDeclareFields": true }],
+    "syntax-class-properties"
+  ]
+}
diff --git a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/output.js b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/output.js
new file mode 100644
index 0000000000..a869c28495
--- /dev/null
+++ b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/class/declare/output.js
@@ -0,0 +1 @@
+class A {}
diff --git a/packages/babel-preset-flow/src/index.js b/packages/babel-preset-flow/src/index.js
index 6fbd56a196..da02e7e6c0 100644
--- a/packages/babel-preset-flow/src/index.js
+++ b/packages/babel-preset-flow/src/index.js
@@ -1,10 +1,10 @@
 import { declare } from "@babel/helper-plugin-utils";
 import transformFlowStripTypes from "@babel/plugin-transform-flow-strip-types";
 
-export default declare((api, { all }) => {
+export default declare((api, { all, allowDeclareFields }) => {
   api.assertVersion(7);
 
   return {
-    plugins: [[transformFlowStripTypes, { all }]],
+    plugins: [[transformFlowStripTypes, { all, allowDeclareFields }]],
   };
 });