diff --git a/packages/babel-generator/src/generators/classes.js b/packages/babel-generator/src/generators/classes.js
index 1649cdee39..da1b14f78e 100644
--- a/packages/babel-generator/src/generators/classes.js
+++ b/packages/babel-generator/src/generators/classes.js
@@ -117,6 +117,21 @@ export function ClassProperty(node: Object) {
   this.semicolon();
 }
 
+export function ClassPrivateProperty(node: Object) {
+  if (node.static) {
+    this.word("static");
+    this.space();
+  }
+  this.print(node.key, node);
+  if (node.value) {
+    this.space();
+    this.token("=");
+    this.space();
+    this.print(node.value, node);
+  }
+  this.semicolon();
+}
+
 export function ClassMethod(node: Object) {
   this._classMethodHead(node);
   this.space();
diff --git a/packages/babel-generator/src/generators/expressions.js b/packages/babel-generator/src/generators/expressions.js
index e85eec6538..2a7fc66e2e 100644
--- a/packages/babel-generator/src/generators/expressions.js
+++ b/packages/babel-generator/src/generators/expressions.js
@@ -254,3 +254,8 @@ export function MetaProperty(node: Object) {
   this.token(".");
   this.print(node.property, node);
 }
+
+export function PrivateName(node: Object) {
+  this.token("#");
+  this.print(node.id, node);
+}
diff --git a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js
index 41176ad01b..6256942ca5 100644
--- a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js
+++ b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/input.js
@@ -26,6 +26,11 @@ class Foo {
   async;
   foo; bar;
   foo = 0; bar = 1;
+
+  #foo;
+  #foo = 1;
+  static #foo;
+  static #foo = Foo.#foo;
 }
 
 class A1 {
diff --git a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/options.json b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/options.json
index 24551b8170..a437d2af54 100644
--- a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/options.json
+++ b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/options.json
@@ -1 +1 @@
-{ "plugins": ["classProperties"] }
\ No newline at end of file
+{ "plugins": ["classProperties", "classPrivateProperties"] }
diff --git a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js
index 0c686caa32..905fe31bdb 100644
--- a/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js
+++ b/packages/babel-generator/test/fixtures/types/ClassBody-ClassProperty/output.js
@@ -26,6 +26,10 @@ class Foo {
   bar;
   foo = 0;
   bar = 1;
+  #foo;
+  #foo = 1;
+  static #foo;
+  static #foo = Foo.#foo;
 }
 
 class A1 {
@@ -65,4 +69,4 @@ class A6 {
 class A7 {
   static get static() {}
 
-}
\ No newline at end of file
+}
diff --git a/packages/babel-helper-define-map/src/index.js b/packages/babel-helper-define-map/src/index.js
index 850bd51adb..ff588c1ce3 100644
--- a/packages/babel-helper-define-map/src/index.js
+++ b/packages/babel-helper-define-map/src/index.js
@@ -61,7 +61,7 @@ export function push(
     key = t.toComputedKey(node, node.key);
   }
 
-  if (t.isObjectProperty(node) || t.isClassProperty(node)) {
+  if (t.isProperty(node)) {
     value = node.value;
   } else if (t.isObjectMethod(node) || t.isClassMethod(node)) {
     value = t.functionExpression(
@@ -131,15 +131,12 @@ export function toClassObject(mutatorMap: Object): Object {
     const propNode = t.objectProperty(map._key, mapNode, map._computed);
 
     Object.keys(map).forEach(function(key) {
-      let node = map[key];
+      const node = map[key];
       if (key[0] === "_") return;
 
-      const inheritNode = node;
-      if (t.isClassMethod(node) || t.isClassProperty(node)) node = node.value;
-
       const prop = t.objectProperty(t.identifier(key), node);
-      t.inheritsComments(prop, inheritNode);
-      t.removeComments(inheritNode);
+      t.inheritsComments(prop, node);
+      t.removeComments(node);
 
       mapNode.properties.push(prop);
     });
diff --git a/packages/babel-plugin-syntax-class-properties/src/index.js b/packages/babel-plugin-syntax-class-properties/src/index.js
index 8f4ee10929..fc3f176e03 100644
--- a/packages/babel-plugin-syntax-class-properties/src/index.js
+++ b/packages/babel-plugin-syntax-class-properties/src/index.js
@@ -5,7 +5,7 @@ export default declare(api => {
 
   return {
     manipulateOptions(opts, parserOpts) {
-      parserOpts.plugins.push("classProperties");
+      parserOpts.plugins.push("classProperties", "classPrivateProperties");
     },
   };
 });
diff --git a/packages/babel-plugin-transform-parameters/src/rest.js b/packages/babel-plugin-transform-parameters/src/rest.js
index aa3a8885fb..4f0817b857 100644
--- a/packages/babel-plugin-transform-parameters/src/rest.js
+++ b/packages/babel-plugin-transform-parameters/src/rest.js
@@ -46,7 +46,7 @@ const memberExpressionOptimisationVisitor = {
     path.skip();
   },
 
-  "Function|ClassProperty": function(path, state) {
+  Function(path, state) {
     // Detect whether any reference to rest is contained in nested functions to
     // determine if deopt is necessary.
     const oldNoOptimise = state.noOptimise;
diff --git a/packages/babel-plugin-transform-parameters/test/fixtures/parameters/rest-arrow-functions/input.js b/packages/babel-plugin-transform-parameters/test/fixtures/parameters/rest-arrow-functions/input.js
index 80988d02b6..9cedf94796 100644
--- a/packages/babel-plugin-transform-parameters/test/fixtures/parameters/rest-arrow-functions/input.js
+++ b/packages/babel-plugin-transform-parameters/test/fixtures/parameters/rest-arrow-functions/input.js
@@ -33,4 +33,4 @@ var innerclassproperties = (...args) => (
     static args = args;
     args = args;
   }
-);
\ No newline at end of file
+);
diff --git a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/destructure/output.js b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/destructure/output.js
index f13ad91a47..e33d215b94 100644
--- a/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/destructure/output.js
+++ b/packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/destructure/output.js
@@ -1,8 +1,8 @@
 class AnchorLink extends Component {
   render() {
-    const _props = this.props,
-          isExternal = _props.isExternal,
-          children = _props.children;
+    const _this$props = this.props,
+          isExternal = _this$props.isExternal,
+          children = _this$props.children;
 
     if (isExternal) {
       return <a>{children}</a>;
diff --git a/packages/babel-traverse/src/path/conversion.js b/packages/babel-traverse/src/path/conversion.js
index ca8b144942..b192b4d9d5 100644
--- a/packages/babel-traverse/src/path/conversion.js
+++ b/packages/babel-traverse/src/path/conversion.js
@@ -163,12 +163,13 @@ function hoistFunctionEnvironment(
   specCompliant = false,
   allowInsertArrow = true,
 ) {
-  const thisEnvFn = fnPath.findParent(
-    p =>
+  const thisEnvFn = fnPath.findParent(p => {
+    return (
       (p.isFunction() && !p.isArrowFunctionExpression()) ||
       p.isProgram() ||
-      p.isClassProperty({ static: false }),
-  );
+      p.isClassProperty({ static: false })
+    );
+  });
   const inConstructor = thisEnvFn && thisEnvFn.node.kind === "constructor";
 
   if (thisEnvFn.isClassProperty()) {
diff --git a/packages/babel-traverse/src/scope/index.js b/packages/babel-traverse/src/scope/index.js
index a2055dd05a..4603f326e3 100644
--- a/packages/babel-traverse/src/scope/index.js
+++ b/packages/babel-traverse/src/scope/index.js
@@ -36,6 +36,10 @@ function gatherNodeParts(node: Object, parts: Array) {
     for (const prop of (node.properties: Array)) {
       gatherNodeParts(prop.key || prop.argument, parts);
     }
+  } else if (t.isPrivateName(node)) {
+    gatherNodeParts(node.id, parts);
+  } else if (t.isThisExpression(node)) {
+    parts.push("this");
   }
 }
 
@@ -622,7 +626,7 @@ export default class Scope {
       if (node.computed && !this.isPure(node.key, constantsOnly)) return false;
       if (node.kind === "get" || node.kind === "set") return false;
       return true;
-    } else if (t.isClassProperty(node) || t.isObjectProperty(node)) {
+    } else if (t.isProperty(node)) {
       if (node.computed && !this.isPure(node.key, constantsOnly)) return false;
       return this.isPure(node.value, constantsOnly);
     } else if (t.isUnaryExpression(node)) {
diff --git a/packages/babel-types/README.md b/packages/babel-types/README.md
index 51b2183103..aaee40e532 100644
--- a/packages/babel-types/README.md
+++ b/packages/babel-types/README.md
@@ -256,7 +256,7 @@ t.classBody(body)
 
 See also `t.isClassBody(node, opts)` and `t.assertClassBody(node, opts)`.
 
- - `body`: `Array<ClassMethod | ClassProperty | TSDeclareMethod | TSIndexSignature>` (required)
+ - `body`: `Array<ClassMethod | ClassProperty | ClassPrivateProperty | TSDeclareMethod | TSIndexSignature>` (required)
 
 ---
 
@@ -343,6 +343,20 @@ Aliases: `Function`, `Scopable`, `BlockParent`, `FunctionParent`, `Method`
 
 ---
 
+### classPrivateProperty
+```javascript
+t.classPrivateProperty(key, value)
+```
+
+See also `t.isClassPrivateProperty(node, opts)` and `t.assertClassPrivateProperty(node, opts)`.
+
+Aliases: `Property`, `Private`
+
+ - `key`: `PrivateName` (required)
+ - `value`: `Expression` (default: `null`)
+
+---
+
 ### classProperty
 ```javascript
 t.classProperty(key, value, typeAnnotation, decorators, computed)
@@ -1636,6 +1650,19 @@ Aliases: `Expression`, `ExpressionWrapper`
 
 ---
 
+### privateName
+```javascript
+t.privateName(id)
+```
+
+See also `t.isPrivateName(node, opts)` and `t.assertPrivateName(node, opts)`.
+
+Aliases: `Private`
+
+ - `id`: `Identifier` (required)
+
+---
+
 ### program
 ```javascript
 t.program(body, directives, sourceType)
diff --git a/packages/babel-types/src/asserts/generated/index.js b/packages/babel-types/src/asserts/generated/index.js
index efae53080e..bfc46770eb 100644
--- a/packages/babel-types/src/asserts/generated/index.js
+++ b/packages/babel-types/src/asserts/generated/index.js
@@ -663,6 +663,12 @@ export function assertOptionalCallExpression(
 ): void {
   assert("OptionalCallExpression", node, opts);
 }
+export function assertClassPrivateProperty(
+  node: Object,
+  opts?: Object = {},
+): void {
+  assert("ClassPrivateProperty", node, opts);
+}
 export function assertImport(node: Object, opts?: Object = {}): void {
   assert("Import", node, opts);
 }
@@ -684,6 +690,9 @@ export function assertExportNamespaceSpecifier(
 ): void {
   assert("ExportNamespaceSpecifier", node, opts);
 }
+export function assertPrivateName(node: Object, opts?: Object = {}): void {
+  assert("PrivateName", node, opts);
+}
 export function assertTSParameterProperty(
   node: Object,
   opts?: Object = {},
@@ -1059,6 +1068,9 @@ export function assertFlowPredicate(node: Object, opts?: Object = {}): void {
 export function assertJSX(node: Object, opts?: Object = {}): void {
   assert("JSX", node, opts);
 }
+export function assertPrivate(node: Object, opts?: Object = {}): void {
+  assert("Private", node, opts);
+}
 export function assertTSTypeElement(node: Object, opts?: Object = {}): void {
   assert("TSTypeElement", node, opts);
 }
diff --git a/packages/babel-types/src/builders/generated/index.js b/packages/babel-types/src/builders/generated/index.js
index 1ec3b17766..b3c07aa47d 100644
--- a/packages/babel-types/src/builders/generated/index.js
+++ b/packages/babel-types/src/builders/generated/index.js
@@ -604,6 +604,10 @@ export function OptionalCallExpression(...args: Array<any>): Object {
   return builder("OptionalCallExpression", ...args);
 }
 export { OptionalCallExpression as optionalCallExpression };
+export function ClassPrivateProperty(...args: Array<any>): Object {
+  return builder("ClassPrivateProperty", ...args);
+}
+export { ClassPrivateProperty as classPrivateProperty };
 export function Import(...args: Array<any>): Object {
   return builder("Import", ...args);
 }
@@ -624,6 +628,10 @@ export function ExportNamespaceSpecifier(...args: Array<any>): Object {
   return builder("ExportNamespaceSpecifier", ...args);
 }
 export { ExportNamespaceSpecifier as exportNamespaceSpecifier };
+export function PrivateName(...args: Array<any>): Object {
+  return builder("PrivateName", ...args);
+}
+export { PrivateName as privateName };
 export function TSParameterProperty(...args: Array<any>): Object {
   return builder("TSParameterProperty", ...args);
 }
diff --git a/packages/babel-types/src/constants/generated/index.js b/packages/babel-types/src/constants/generated/index.js
index ea64f77d1e..eedb7038ed 100644
--- a/packages/babel-types/src/constants/generated/index.js
+++ b/packages/babel-types/src/constants/generated/index.js
@@ -46,5 +46,6 @@ export const FLOWBASEANNOTATION_TYPES =
 export const FLOWDECLARATION_TYPES = FLIPPED_ALIAS_KEYS["FlowDeclaration"];
 export const FLOWPREDICATE_TYPES = FLIPPED_ALIAS_KEYS["FlowPredicate"];
 export const JSX_TYPES = FLIPPED_ALIAS_KEYS["JSX"];
+export const PRIVATE_TYPES = FLIPPED_ALIAS_KEYS["Private"];
 export const TSTYPEELEMENT_TYPES = FLIPPED_ALIAS_KEYS["TSTypeElement"];
 export const TSTYPE_TYPES = FLIPPED_ALIAS_KEYS["TSType"];
diff --git a/packages/babel-types/src/definitions/core.js b/packages/babel-types/src/definitions/core.js
index 0bd5c2ae33..ab1e8b70b3 100644
--- a/packages/babel-types/src/definitions/core.js
+++ b/packages/babel-types/src/definitions/core.js
@@ -503,7 +503,7 @@ defineType("MemberExpression", {
     },
     property: {
       validate: (function() {
-        const normal = assertNodeType("Identifier");
+        const normal = assertNodeType("Identifier", "PrivateName");
         const computed = assertNodeType("Expression");
 
         return function(node, key, val) {
diff --git a/packages/babel-types/src/definitions/es2015.js b/packages/babel-types/src/definitions/es2015.js
index f5c67810f3..26c0d4a344 100644
--- a/packages/babel-types/src/definitions/es2015.js
+++ b/packages/babel-types/src/definitions/es2015.js
@@ -88,6 +88,7 @@ defineType("ClassBody", {
           assertNodeType(
             "ClassMethod",
             "ClassProperty",
+            "ClassPrivateProperty",
             "TSDeclareMethod",
             "TSIndexSignature",
           ),
diff --git a/packages/babel-types/src/definitions/experimental.js b/packages/babel-types/src/definitions/experimental.js
index c9d7b1a301..7b22fa0a04 100644
--- a/packages/babel-types/src/definitions/experimental.js
+++ b/packages/babel-types/src/definitions/experimental.js
@@ -115,6 +115,21 @@ defineType("OptionalCallExpression", {
   },
 });
 
+defineType("ClassPrivateProperty", {
+  visitor: ["key", "value"],
+  builder: ["key", "value"],
+  aliases: ["Property", "Private"],
+  fields: {
+    key: {
+      validate: assertNodeType("PrivateName"),
+    },
+    value: {
+      validate: assertNodeType("Expression"),
+      optional: true,
+    },
+  },
+});
+
 defineType("Import", {
   aliases: ["Expression"],
 });
@@ -157,3 +172,13 @@ defineType("ExportNamespaceSpecifier", {
     },
   },
 });
+
+defineType("PrivateName", {
+  visitor: ["id"],
+  aliases: ["Private"],
+  fields: {
+    id: {
+      validate: assertNodeType("Identifier"),
+    },
+  },
+});
diff --git a/packages/babel-types/src/validators/generated/index.js b/packages/babel-types/src/validators/generated/index.js
index 874d8f6508..48729135bf 100644
--- a/packages/babel-types/src/validators/generated/index.js
+++ b/packages/babel-types/src/validators/generated/index.js
@@ -494,6 +494,9 @@ export function isOptionalMemberExpression(
 export function isOptionalCallExpression(node: Object, opts?: Object): boolean {
   return is("OptionalCallExpression", node, opts);
 }
+export function isClassPrivateProperty(node: Object, opts?: Object): boolean {
+  return is("ClassPrivateProperty", node, opts);
+}
 export function isImport(node: Object, opts?: Object): boolean {
   return is("Import", node, opts);
 }
@@ -512,6 +515,9 @@ export function isExportNamespaceSpecifier(
 ): boolean {
   return is("ExportNamespaceSpecifier", node, opts);
 }
+export function isPrivateName(node: Object, opts?: Object): boolean {
+  return is("PrivateName", node, opts);
+}
 export function isTSParameterProperty(node: Object, opts?: Object): boolean {
   return is("TSParameterProperty", node, opts);
 }
@@ -821,6 +827,9 @@ export function isFlowPredicate(node: Object, opts?: Object): boolean {
 export function isJSX(node: Object, opts?: Object): boolean {
   return is("JSX", node, opts);
 }
+export function isPrivate(node: Object, opts?: Object): boolean {
+  return is("Private", node, opts);
+}
 export function isTSTypeElement(node: Object, opts?: Object): boolean {
   return is("TSTypeElement", node, opts);
 }
diff --git a/packages/babel-types/src/validators/isReferenced.js b/packages/babel-types/src/validators/isReferenced.js
index 1944665e9d..076bbb272d 100644
--- a/packages/babel-types/src/validators/isReferenced.js
+++ b/packages/babel-types/src/validators/isReferenced.js
@@ -76,8 +76,9 @@ export default function isReferenced(node: Object, parent: Object): boolean {
     // yes: class { [NODE] = value; }
     // yes: class { key = NODE; }
     case "ClassProperty":
+    case "ClassPrivateProperty":
       if (parent.key === node) {
-        return parent.computed;
+        return !!parent.computed;
       } else {
         return parent.value === node;
       }