diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 59007e610b4ad..be96d3de07dd8 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -4280,5 +4280,9 @@
     "Remove all unused labels": {
         "category": "Message",
         "code": 95054
+    },
+    "Convert '{0}' to mapped object type": {
+        "category": "Message",
+        "code": 95055
     }
 }
diff --git a/src/harness/tsconfig.json b/src/harness/tsconfig.json
index 359701a02cb3a..08b8acadc9374 100644
--- a/src/harness/tsconfig.json
+++ b/src/harness/tsconfig.json
@@ -118,6 +118,7 @@
         "../services/codefixes/requireInTs.ts",
         "../services/codefixes/useDefaultImport.ts",
         "../services/codefixes/fixAddModuleReferTypeMissingTypeof.ts",
+        "../services/codefixes/convertToMappedObjectType.ts",
         "../services/refactors/extractSymbol.ts",
         "../services/refactors/generateGetAccessorAndSetAccessor.ts",
         "../services/refactors/moveToNewFile.ts",
diff --git a/src/server/tsconfig.json b/src/server/tsconfig.json
index 8ae6974baf062..806721c9c56f3 100644
--- a/src/server/tsconfig.json
+++ b/src/server/tsconfig.json
@@ -114,6 +114,7 @@
         "../services/codefixes/requireInTs.ts",
         "../services/codefixes/useDefaultImport.ts",
         "../services/codefixes/fixAddModuleReferTypeMissingTypeof.ts",
+        "../services/codefixes/convertToMappedObjectType.ts",
         "../services/refactors/extractSymbol.ts",
         "../services/refactors/generateGetAccessorAndSetAccessor.ts",
         "../services/refactors/moveToNewFile.ts",
diff --git a/src/server/tsconfig.library.json b/src/server/tsconfig.library.json
index 922af11e87963..cabcd8ff104ed 100644
--- a/src/server/tsconfig.library.json
+++ b/src/server/tsconfig.library.json
@@ -120,6 +120,7 @@
         "../services/codefixes/requireInTs.ts",
         "../services/codefixes/useDefaultImport.ts",
         "../services/codefixes/fixAddModuleReferTypeMissingTypeof.ts",
+        "../services/codefixes/convertToMappedObjectType.ts",
         "../services/refactors/extractSymbol.ts",
         "../services/refactors/generateGetAccessorAndSetAccessor.ts",
         "../services/refactors/moveToNewFile.ts",
diff --git a/src/services/codefixes/convertToMappedObjectType.ts b/src/services/codefixes/convertToMappedObjectType.ts
new file mode 100644
index 0000000000000..b8315ce6d96da
--- /dev/null
+++ b/src/services/codefixes/convertToMappedObjectType.ts
@@ -0,0 +1,94 @@
+/* @internal */
+namespace ts.codefix {
+    const fixIdAddMissingTypeof = "fixConvertToMappedObjectType";
+    const fixId = fixIdAddMissingTypeof;
+    const errorCodes = [Diagnostics.An_index_signature_parameter_type_cannot_be_a_union_type_Consider_using_a_mapped_object_type_instead.code];
+
+    type FixableDeclaration = InterfaceDeclaration | TypeAliasDeclaration;
+
+    interface Info {
+        indexSignature: IndexSignatureDeclaration;
+        container: FixableDeclaration;
+        otherMembers: ReadonlyArray<TypeElement>;
+        parameterName: Identifier;
+        parameterType: TypeNode;
+    }
+
+    registerCodeFix({
+        errorCodes,
+        getCodeActions: context => {
+            const { sourceFile, span } = context;
+            const info = getFixableSignatureAtPosition(sourceFile, span.start);
+            if (!info) return;
+            const { indexSignature, container, otherMembers, parameterName, parameterType } = info;
+
+            const changes = textChanges.ChangeTracker.with(context, t => doChange(t, sourceFile, indexSignature, container, otherMembers, parameterName, parameterType));
+            return [createCodeFixAction(fixId, changes, [Diagnostics.Convert_0_to_mapped_object_type, idText(container.name)], fixId, [Diagnostics.Convert_0_to_mapped_object_type, idText(container.name)])];
+        },
+        fixIds: [fixId],
+        getAllCodeActions: context => codeFixAll(context, errorCodes, (changes, diag) => {
+            const info = getFixableSignatureAtPosition(diag.file, diag.start);
+            if (!info) return;
+            const { indexSignature, container, otherMembers, parameterName, parameterType } = info;
+
+            doChange(changes, context.sourceFile, indexSignature, container, otherMembers, parameterName, parameterType);
+        })
+    });
+
+    function isFixableParameterName(node: Node): boolean {
+        return node && node.parent && node.parent.parent && node.parent.parent.parent && !isClassDeclaration(node.parent.parent.parent);
+    }
+
+    function getFixableSignatureAtPosition(sourceFile: SourceFile, pos: number): Info | undefined {
+        const token = getTokenAtPosition(sourceFile, pos, /*includeJsDocComment*/ false);
+        if (!isFixableParameterName(token)) return undefined;
+
+        const indexSignature = <IndexSignatureDeclaration>token.parent.parent;
+        const container = isInterfaceDeclaration(indexSignature.parent) ? indexSignature.parent : <TypeAliasDeclaration>indexSignature.parent.parent;
+        const members = isInterfaceDeclaration(container) ? container.members : (<TypeLiteralNode>container.type).members;
+        const otherMembers = filter(members, member => !isIndexSignatureDeclaration(member));
+        const parameter = first(indexSignature.parameters);
+
+        return {
+            indexSignature,
+            container,
+            otherMembers,
+            parameterName: <Identifier>parameter.name,
+            parameterType: parameter.type!
+        };
+    }
+
+    function getInterfaceHeritageClauses(declaration: FixableDeclaration): NodeArray<ExpressionWithTypeArguments> | undefined {
+        if (!isInterfaceDeclaration(declaration)) return undefined;
+
+        const heritageClause = getHeritageClause(declaration.heritageClauses, SyntaxKind.ExtendsKeyword);
+        return heritageClause && heritageClause.types;
+    }
+
+    function createTypeAliasFromInterface(indexSignature: IndexSignatureDeclaration, declaration: FixableDeclaration, otherMembers: ReadonlyArray<TypeElement>, parameterName: Identifier, parameterType: TypeNode) {
+        const heritageClauses = getInterfaceHeritageClauses(declaration);
+        const mappedTypeParameter = createTypeParameterDeclaration(parameterName, parameterType);
+        const mappedIntersectionType = createMappedTypeNode(
+            hasReadonlyModifier(indexSignature) ? createModifier(SyntaxKind.ReadonlyKeyword) : undefined,
+            mappedTypeParameter,
+            indexSignature.questionToken,
+            indexSignature.type);
+
+        return createTypeAliasDeclaration(
+            declaration.decorators,
+            declaration.modifiers,
+            declaration.name,
+            declaration.typeParameters,
+            createIntersectionTypeNode(
+                concatenate(
+                    heritageClauses,
+                    append<TypeNode>([mappedIntersectionType], otherMembers.length ? createTypeLiteralNode(otherMembers) : undefined)
+                )
+            )
+        );
+    }
+
+    function doChange(changes: textChanges.ChangeTracker, sourceFile: SourceFile, indexSignature: IndexSignatureDeclaration, declaration: FixableDeclaration, otherMembers: ReadonlyArray<TypeElement>, parameterName: Identifier, parameterType: TypeNode) {
+        changes.replaceNode(sourceFile, declaration, createTypeAliasFromInterface(indexSignature, declaration, otherMembers, parameterName, parameterType));
+    }
+}
diff --git a/src/services/refactors/generateGetAccessorAndSetAccessor.ts b/src/services/refactors/generateGetAccessorAndSetAccessor.ts
index 6b49b84d4de3d..07104f8e6204c 100644
--- a/src/services/refactors/generateGetAccessorAndSetAccessor.ts
+++ b/src/services/refactors/generateGetAccessorAndSetAccessor.ts
@@ -88,7 +88,7 @@ namespace ts.refactor.generateGetAccessorAndSetAccessor {
         return { renameFilename, renameLocation, edits };
     }
 
-    function isConvertableName (name: DeclarationName): name is AcceptedNameType {
+    function isConvertibleName (name: DeclarationName): name is AcceptedNameType {
         return isIdentifier(name) || isStringLiteral(name);
     }
 
@@ -125,7 +125,7 @@ namespace ts.refactor.generateGetAccessorAndSetAccessor {
         // make sure declaration have AccessibilityModifier or Static Modifier or Readonly Modifier
         const meaning = ModifierFlags.AccessibilityModifier | ModifierFlags.Static | ModifierFlags.Readonly;
         if (!declaration || !rangeOverlapsWithStartEnd(declaration.name, startPosition, endPosition!) // TODO: GH#18217
-            || !isConvertableName(declaration.name) || (getModifierFlags(declaration) | meaning) !== meaning) return undefined;
+            || !isConvertibleName(declaration.name) || (getModifierFlags(declaration) | meaning) !== meaning) return undefined;
 
         const name = declaration.name.text;
         const startWithUnderscore = startsWithUnderscore(name);
diff --git a/src/services/tsconfig.json b/src/services/tsconfig.json
index 7e1ccc9c3afc0..960e46fb367a1 100644
--- a/src/services/tsconfig.json
+++ b/src/services/tsconfig.json
@@ -111,6 +111,7 @@
         "codefixes/requireInTs.ts",
         "codefixes/useDefaultImport.ts",
         "codefixes/fixAddModuleReferTypeMissingTypeof.ts",
+        "codefixes/convertToMappedObjectType.ts",
         "refactors/extractSymbol.ts",
         "refactors/generateGetAccessorAndSetAccessor.ts",
         "refactors/moveToNewFile.ts",
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType1.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType1.ts
new file mode 100644
index 0000000000000..f00702e7bdc04
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType1.ts
@@ -0,0 +1,17 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface SomeType {
+////     a: string;
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+type SomeType = {
+    [prop in K]: any;
+} & {
+    a: string;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType10.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType10.ts
new file mode 100644
index 0000000000000..073b20d91608f
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType10.ts
@@ -0,0 +1,23 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface Foo { }
+//// interface Bar<T> { bar: T; }
+//// interface SomeType<T> extends Foo, Bar<T> {
+////     a: number;
+////     b: T;
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+interface Foo { }
+interface Bar<T> { bar: T; }
+type SomeType<T> = Foo & Bar<T> & {
+    [prop in K]: any;
+} & {
+    a: number;
+    b: T;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType11.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType11.ts
new file mode 100644
index 0000000000000..b82ee1ac179e7
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType11.ts
@@ -0,0 +1,23 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface Foo { }
+//// interface Bar<T> { bar: T; }
+//// interface SomeType<T> extends Foo, Bar<T> {
+////     a: number;
+////     b: T;
+////     readonly [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+interface Foo { }
+interface Bar<T> { bar: T; }
+type SomeType<T> = Foo & Bar<T> & {
+    readonly [prop in K]: any;
+} & {
+    a: number;
+    b: T;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType12.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType12.ts
new file mode 100644
index 0000000000000..6374dc43dacb4
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType12.ts
@@ -0,0 +1,12 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface Foo { }
+//// interface Bar<T> { bar: T; }
+//// interface SomeType<T> extends Foo, Bar<T> {
+////     a: number;
+////     b: T;
+////     readonly [prop: K]?: any;
+//// }
+
+verify.not.codeFixAvailable()
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType2.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType2.ts
new file mode 100644
index 0000000000000..27dfc7cab0d56
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType2.ts
@@ -0,0 +1,17 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// type SomeType = {
+////     a: string;
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+type SomeType = {
+    [prop in K]: any;
+} & {
+    a: string;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType3.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType3.ts
new file mode 100644
index 0000000000000..b916eaca9b62f
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType3.ts
@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// type SomeType = {
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+type SomeType = {
+    [prop in K]: any;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType4.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType4.ts
new file mode 100644
index 0000000000000..4077a7c04af28
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType4.ts
@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface SomeType {
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+type SomeType = {
+    [prop in K]: any;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType5.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType5.ts
new file mode 100644
index 0000000000000..869974f9ad2ff
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType5.ts
@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// class SomeType {
+////     [prop: K]: any;
+//// }
+
+verify.not.codeFixAvailable()
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType6.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType6.ts
new file mode 100644
index 0000000000000..b00f356b48b45
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType6.ts
@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface Foo { }
+//// interface SomeType extends Foo {
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+interface Foo { }
+type SomeType = Foo & {
+    [prop in K]: any;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType7.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType7.ts
new file mode 100644
index 0000000000000..a0a1e4eeccb69
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType7.ts
@@ -0,0 +1,18 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface Foo { }
+//// interface Bar { }
+//// interface SomeType extends Foo, Bar {
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+interface Foo { }
+interface Bar { }
+type SomeType = Foo & Bar & {
+    [prop in K]: any;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType8.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType8.ts
new file mode 100644
index 0000000000000..6ee6c9f0aadde
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType8.ts
@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface Foo { }
+//// interface Bar { }
+//// interface SomeType extends Foo, Bar {
+////     a: number;
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+interface Foo { }
+interface Bar { }
+type SomeType = Foo & Bar & {
+    [prop in K]: any;
+} & {
+    a: number;
+};`
+})
diff --git a/tests/cases/fourslash/codeFixConvertToMappedObjectType9.ts b/tests/cases/fourslash/codeFixConvertToMappedObjectType9.ts
new file mode 100644
index 0000000000000..095296481f57d
--- /dev/null
+++ b/tests/cases/fourslash/codeFixConvertToMappedObjectType9.ts
@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+//// type K = "foo" | "bar";
+//// interface Foo { }
+//// interface Bar<T> { bar: T; }
+//// interface SomeType extends Foo, Bar<number> {
+////     a: number;
+////     [prop: K]: any;
+//// }
+
+verify.codeFix({
+    description: `Convert 'SomeType' to mapped object type`,
+    newFileContent: `type K = "foo" | "bar";
+interface Foo { }
+interface Bar<T> { bar: T; }
+type SomeType = Foo & Bar<number> & {
+    [prop in K]: any;
+} & {
+    a: number;
+};`
+})