diff --git a/codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.ts b/codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.ts
index cb7ae05910d8..50a18d9bd0b0 100644
--- a/codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.ts
+++ b/codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.ts
@@ -1,6 +1,7 @@
 import syntaxObjectRestSpread from "@babel/plugin-syntax-object-rest-spread";
+import type { PluginAPI, PluginObject } from "@babel/core";
 
-export default function ({ types: t }) {
+export default function ({ types: t }: PluginAPI): PluginObject {
   return {
     inherits: syntaxObjectRestSpread.default,
 
@@ -21,10 +22,15 @@ export default function ({ types: t }) {
           const arg = args[i];
           const { node } = arg;
 
-          if (arg.isObjectExpression()) {
+          if (t.isObjectExpression(node)) {
             properties.push(...node.properties);
           } else {
-            properties.push(t.spreadElement(node));
+            properties.push(
+              t.spreadElement(
+                // @ts-expect-error fixme
+                node,
+              ),
+            );
           }
         }
 
diff --git a/codemods/babel-plugin-codemod-optional-catch-binding/src/index.ts b/codemods/babel-plugin-codemod-optional-catch-binding/src/index.ts
index d4873469bb7a..9cf2954e0e58 100644
--- a/codemods/babel-plugin-codemod-optional-catch-binding/src/index.ts
+++ b/codemods/babel-plugin-codemod-optional-catch-binding/src/index.ts
@@ -1,6 +1,7 @@
 import syntaxOptionalCatchBinding from "@babel/plugin-syntax-optional-catch-binding";
+import type { PluginAPI, PluginObject } from "@babel/core";
 
-export default function ({ types: t }) {
+export default function ({ types: t }: PluginAPI): PluginObject {
   return {
     inherits: syntaxOptionalCatchBinding.default,
 
diff --git a/packages/babel-core/src/config/index.ts b/packages/babel-core/src/config/index.ts
index d231a8ec6d59..aff0cc5b7fd2 100644
--- a/packages/babel-core/src/config/index.ts
+++ b/packages/babel-core/src/config/index.ts
@@ -18,7 +18,10 @@ type PluginAPI = basePluginAPI & typeof import("..");
 type PresetAPI = basePresetAPI & typeof import("..");
 export type { PluginAPI, PresetAPI };
 // todo: may need to refine PresetObject to be a subset of ValidatedOptions
-export type { ValidatedOptions as PresetObject } from "./validation/options";
+export type {
+  CallerMetadata,
+  ValidatedOptions as PresetObject,
+} from "./validation/options";
 
 import loadFullConfig from "./full";
 import { loadPartialConfig as loadPartialConfigRunner } from "./partial";
diff --git a/packages/babel-core/src/index.ts b/packages/babel-core/src/index.ts
index cdbc2e6998bb..fdebb2cd1a4c 100644
--- a/packages/babel-core/src/index.ts
+++ b/packages/babel-core/src/index.ts
@@ -30,6 +30,8 @@ export {
 } from "./config";
 
 export type {
+  CallerMetadata,
+  InputOptions,
   PluginAPI,
   PluginObject,
   PresetAPI,
diff --git a/packages/babel-plugin-transform-runtime/src/get-runtime-path/browser.ts b/packages/babel-plugin-transform-runtime/src/get-runtime-path/browser.ts
index 94af79f4ce4d..53cc0f75469c 100644
--- a/packages/babel-plugin-transform-runtime/src/get-runtime-path/browser.ts
+++ b/packages/babel-plugin-transform-runtime/src/get-runtime-path/browser.ts
@@ -1,4 +1,8 @@
-export default function (moduleName, dirname, absoluteRuntime) {
+export default function (
+  moduleName: string,
+  dirname: string,
+  absoluteRuntime: string | boolean,
+) {
   if (absoluteRuntime === false) return moduleName;
 
   resolveFSPath();
diff --git a/packages/babel-plugin-transform-runtime/src/get-runtime-path/index.ts b/packages/babel-plugin-transform-runtime/src/get-runtime-path/index.ts
index 37fdc83a6827..ac92873a8e05 100644
--- a/packages/babel-plugin-transform-runtime/src/get-runtime-path/index.ts
+++ b/packages/babel-plugin-transform-runtime/src/get-runtime-path/index.ts
@@ -3,7 +3,11 @@ import path from "path";
 import { createRequire } from "module";
 const require = createRequire(import.meta.url);
 
-export default function (moduleName, dirname, absoluteRuntime) {
+export default function (
+  moduleName: string,
+  dirname: string,
+  absoluteRuntime: string | boolean,
+) {
   if (absoluteRuntime === false) return moduleName;
 
   return resolveAbsoluteRuntime(
@@ -33,6 +37,6 @@ function resolveAbsoluteRuntime(moduleName: string, dirname: string) {
   }
 }
 
-export function resolveFSPath(path) {
+export function resolveFSPath(path: string) {
   return require.resolve(path).replace(/\\/g, "/");
 }
diff --git a/packages/babel-plugin-transform-runtime/src/helpers.ts b/packages/babel-plugin-transform-runtime/src/helpers.ts
index ad77e524f9ae..bea33ed07af0 100644
--- a/packages/babel-plugin-transform-runtime/src/helpers.ts
+++ b/packages/babel-plugin-transform-runtime/src/helpers.ts
@@ -1,6 +1,9 @@
 import semver from "semver";
 
-export function hasMinVersion(minVersion, runtimeVersion) {
+export function hasMinVersion(
+  minVersion: string,
+  runtimeVersion: string | void,
+) {
   // If the range is unavailable, we're running the script during Babel's
   // build process, and we want to assume that all versions are satisfied so
   // that the built output will include all definitions.
diff --git a/packages/babel-plugin-transform-runtime/src/index.ts b/packages/babel-plugin-transform-runtime/src/index.ts
index b734e4b6e3fc..d16ea9acae92 100644
--- a/packages/babel-plugin-transform-runtime/src/index.ts
+++ b/packages/babel-plugin-transform-runtime/src/index.ts
@@ -4,6 +4,7 @@ import { types as t } from "@babel/core";
 
 import { hasMinVersion } from "./helpers";
 import getRuntimePath, { resolveFSPath } from "./get-runtime-path";
+import type { PluginAPI, PluginObject, CallerMetadata } from "@babel/core";
 
 import _pluginCorejs2 from "babel-plugin-polyfill-corejs2";
 import _pluginCorejs3 from "babel-plugin-polyfill-corejs3";
@@ -17,7 +18,8 @@ const pluginRegenerator = (_pluginRegenerator.default ||
 
 const pluginsCompat = "#__secret_key__@babel/runtime__compatibility";
 
-function supportsStaticESM(caller) {
+function supportsStaticESM(caller: CallerMetadata | void) {
+  // @ts-ignore TS does not narrow down optional chaining
   return !!caller?.supportsStaticESM;
 }
 
@@ -30,6 +32,35 @@ export interface Options {
   version?: string;
 }
 
+interface CoreJS2PluginOptions {
+  absoluteImports: string | false;
+  method: "usage-pure";
+  [pluginsCompat]: {
+    runtimeVersion: string;
+    useBabelRuntime: string | false;
+    ext: string;
+  };
+}
+
+interface RegeneratorPluginOptions {
+  absoluteImports: string | false;
+  method: "usage-pure";
+  [pluginsCompat]: {
+    useBabelRuntime: string | false;
+  };
+}
+
+interface CoreJS3PluginOptions {
+  absoluteImports: string | false;
+  method: "usage-pure";
+  proposals: boolean;
+  version: number;
+  [pluginsCompat]: {
+    useBabelRuntime: string | false;
+    ext: string;
+  };
+}
+
 export default declare((api, options: Options, dirname) => {
   api.assertVersion(7);
 
@@ -106,11 +137,12 @@ export default declare((api, options: Options, dirname) => {
     var supportsCJSDefault = hasMinVersion(DUAL_MODE_RUNTIME, runtimeVersion);
   }
 
-  function has(obj, key) {
+  function has(obj: {}, key: string) {
     return Object.prototype.hasOwnProperty.call(obj, key);
   }
 
   if (has(options, "useBuiltIns")) {
+    // @ts-expect-error deprecated options
     if (options["useBuiltIns"]) {
       throw new Error(
         "The 'useBuiltIns' option has been removed. The @babel/runtime " +
@@ -125,6 +157,7 @@ export default declare((api, options: Options, dirname) => {
   }
 
   if (has(options, "polyfill")) {
+    // @ts-expect-error deprecated options
     if (options["polyfill"] === false) {
       throw new Error(
         "The 'polyfill' option has been removed. The @babel/runtime " +
@@ -163,8 +196,20 @@ export default declare((api, options: Options, dirname) => {
 
   const modulePath = getRuntimePath(moduleName, dirname, absoluteRuntime);
 
-  function createCorejsPlgin(plugin, options, regeneratorPlugin) {
-    return (api, _, filename) => {
+  function createCorejsPlgin<Options extends {}>(
+    plugin: (
+      api: PluginAPI,
+      options: Options,
+      filename: string,
+    ) => PluginObject,
+    options: Options,
+    regeneratorPlugin: (
+      api: PluginAPI,
+      options: RegeneratorPluginOptions,
+      filename: string,
+    ) => PluginObject,
+  ): (api: PluginAPI, options: {}, filename: string) => PluginObject {
+    return (api: PluginAPI, _: {}, filename: string) => {
       return {
         ...plugin(api, options, filename),
         inherits: regeneratorPlugin,
@@ -173,7 +218,13 @@ export default declare((api, options: Options, dirname) => {
   }
 
   // TODO: Remove this in Babel 8
-  function createRegeneratorPlugin(options) {
+  function createRegeneratorPlugin(
+    options: RegeneratorPluginOptions,
+  ): (
+    api: PluginAPI,
+    options: RegeneratorPluginOptions,
+    filename: string,
+  ) => PluginObject {
     if (!useRuntimeRegenerator) return undefined;
     return (api, _, filename) => {
       return pluginRegenerator(api, options, filename);
@@ -184,7 +235,7 @@ export default declare((api, options: Options, dirname) => {
     name: "transform-runtime",
 
     inherits: injectCoreJS2
-      ? createCorejsPlgin(
+      ? createCorejsPlgin<CoreJS2PluginOptions>(
           pluginCorejs2,
           {
             method: "usage-pure",
@@ -202,7 +253,7 @@ export default declare((api, options: Options, dirname) => {
           }),
         )
       : injectCoreJS3
-      ? createCorejsPlgin(
+      ? createCorejsPlgin<CoreJS3PluginOptions>(
           pluginCorejs3,
           {
             method: "usage-pure",
@@ -226,7 +277,7 @@ export default declare((api, options: Options, dirname) => {
     pre(file) {
       if (!useRuntimeHelpers) return;
 
-      file.set("helperGenerator", name => {
+      file.set("helperGenerator", (name: string) => {
         // If the helper didn't exist yet at the version given, we bail
         // out and let Babel either insert it directly, or throw an error
         // so that plugins can handle that case properly.
@@ -271,9 +322,9 @@ export default declare((api, options: Options, dirname) => {
       const cache = new Map();
 
       function addDefaultImport(
-        source,
-        nameHint,
-        blockHoist,
+        source: string,
+        nameHint: string,
+        blockHoist: number,
         isHelper = false,
       ) {
         // If something on the page adds a helper when the file is an ES6
diff --git a/packages/babel-plugin-transform-typescript/src/enum.ts b/packages/babel-plugin-transform-typescript/src/enum.ts
index 79368a06656a..9a3234286f69 100644
--- a/packages/babel-plugin-transform-typescript/src/enum.ts
+++ b/packages/babel-plugin-transform-typescript/src/enum.ts
@@ -39,7 +39,7 @@ export default function transpileEnum(
       throw new Error(`Unexpected enum parent '${path.parent.type}`);
   }
 
-  function seen(parentPath: NodePath<t.Node>) {
+  function seen(parentPath: NodePath<t.Node>): boolean {
     if (parentPath.isExportDeclaration()) {
       return seen(parentPath.parentPath);
     }
@@ -193,12 +193,12 @@ export function translateEnumValues(
 
 // Based on the TypeScript repository's `evalConstant` in `checker.ts`.
 function evaluate(
-  expr,
+  expr: t.Node,
   seen: PreviousEnumMembers,
 ): number | string | typeof undefined {
   return evalConstant(expr);
 
-  function evalConstant(expr): number | typeof undefined {
+  function evalConstant(expr: t.Node): number | typeof undefined {
     switch (expr.type) {
       case "StringLiteral":
         return expr.value;
@@ -225,7 +225,7 @@ function evaluate(
   function evalUnaryExpression({
     argument,
     operator,
-  }): number | typeof undefined {
+  }: t.UnaryExpression): number | typeof undefined {
     const value = evalConstant(argument);
     if (value === undefined) {
       return undefined;
@@ -243,7 +243,7 @@ function evaluate(
     }
   }
 
-  function evalBinaryExpression(expr): number | typeof undefined {
+  function evalBinaryExpression(expr: t.BinaryExpression): number | undefined {
     const left = evalConstant(expr.left);
     if (left === undefined) {
       return undefined;
diff --git a/packages/babel-plugin-transform-typescript/src/index.ts b/packages/babel-plugin-transform-typescript/src/index.ts
index ef57f17e9e34..01ad3eac6711 100644
--- a/packages/babel-plugin-transform-typescript/src/index.ts
+++ b/packages/babel-plugin-transform-typescript/src/index.ts
@@ -2,7 +2,7 @@ import { declare } from "@babel/helper-plugin-utils";
 import syntaxTypeScript from "@babel/plugin-syntax-typescript";
 import { types as t, template } from "@babel/core";
 import { injectInitialization } from "@babel/helper-create-class-features-plugin";
-import type { NodePath } from "@babel/traverse";
+import type { Binding, NodePath } from "@babel/traverse";
 import type { Options as SyntaxOptions } from "@babel/plugin-syntax-typescript";
 
 import transpileConstEnum from "./const-enum";
@@ -149,7 +149,7 @@ export default declare((api, opts: Options) => {
       if (node.declare) node.declare = null;
       if (node.override) node.override = null;
     },
-    method({ node }) {
+    method({ node }: NodePath<t.ClassMethod | t.ClassPrivateMethod>) {
       if (node.accessibility) node.accessibility = null;
       if (node.abstract) node.abstract = null;
       if (node.optional) node.optional = null;
@@ -157,7 +157,7 @@ export default declare((api, opts: Options) => {
 
       // Rest handled by Function visitor
     },
-    constructor(path, classPath) {
+    constructor(path: NodePath<t.ClassMethod>, classPath: NodePath<t.Class>) {
       if (path.node.accessibility) path.node.accessibility = null;
       // Collects parameter properties so that we can add an assignment
       // for each of them in the constructor body
@@ -487,7 +487,11 @@ export default declare((api, opts: Options) => {
         path.get("body.body").forEach(child => {
           if (child.isClassMethod() || child.isClassPrivateMethod()) {
             if (child.node.kind === "constructor") {
-              classMemberVisitors.constructor(child, path);
+              classMemberVisitors.constructor(
+                // @ts-expect-error A constructor must not be a private method
+                child,
+                path,
+              );
             } else {
               classMemberVisitors.method(child);
             }
@@ -512,7 +516,7 @@ export default declare((api, opts: Options) => {
       },
 
       TSModuleDeclaration(path) {
-        transpileNamespace(path, t, allowNamespaces);
+        transpileNamespace(path, allowNamespaces);
       },
 
       TSInterfaceDeclaration(path) {
@@ -614,7 +618,9 @@ export default declare((api, opts: Options) => {
     return node;
   }
 
-  function visitPattern({ node }) {
+  function visitPattern({
+    node,
+  }: NodePath<t.Identifier | t.Pattern | t.RestElement>) {
     if (node.typeAnnotation) node.typeAnnotation = null;
     if (t.isIdentifier(node) && node.optional) node.optional = null;
     // 'access' and 'readonly' are only for parameter properties, so constructor visitor will handle them.
@@ -625,6 +631,11 @@ export default declare((api, opts: Options) => {
     programPath,
     pragmaImportName,
     pragmaFragImportName,
+  }: {
+    binding: Binding;
+    programPath: NodePath<t.Program>;
+    pragmaImportName: string;
+    pragmaFragImportName: string;
   }) {
     for (const path of binding.referencePaths) {
       if (!isInType(path)) {
diff --git a/packages/babel-plugin-transform-typescript/src/namespace.ts b/packages/babel-plugin-transform-typescript/src/namespace.ts
index 186da7c3c77c..74532eca9412 100644
--- a/packages/babel-plugin-transform-typescript/src/namespace.ts
+++ b/packages/babel-plugin-transform-typescript/src/namespace.ts
@@ -1,29 +1,33 @@
 import { template, types as t } from "@babel/core";
 import type { NodePath } from "@babel/traverse";
 
-export default function transpileNamespace(path, t, allowNamespaces) {
+export default function transpileNamespace(
+  path: NodePath<t.TSModuleDeclaration>,
+  allowNamespaces: boolean,
+) {
   if (path.node.declare || path.node.id.type === "StringLiteral") {
     path.remove();
     return;
   }
 
   if (!allowNamespaces) {
-    throw path.hub.file.buildCodeFrameError(
-      path.node.id,
-      "Namespace not marked type-only declare." +
-        " Non-declarative namespaces are only supported experimentally in Babel." +
-        " To enable and review caveats see:" +
-        " https://babeljs.io/docs/en/babel-plugin-transform-typescript",
-    );
+    throw path
+      .get("id")
+      .buildCodeFrameError(
+        "Namespace not marked type-only declare." +
+          " Non-declarative namespaces are only supported experimentally in Babel." +
+          " To enable and review caveats see:" +
+          " https://babeljs.io/docs/en/babel-plugin-transform-typescript",
+      );
   }
 
   const name = path.node.id.name;
-  const value = handleNested(path, t, t.cloneDeep(path.node));
+  const value = handleNested(path, t.cloneNode(path.node, true));
   const bound = path.scope.hasOwnBinding(name);
   if (path.parent.type === "ExportNamedDeclaration") {
     if (!bound) {
       path.parentPath.insertAfter(value);
-      path.replaceWith(getDeclaration(t, name));
+      path.replaceWith(getDeclaration(name));
       path.scope.registerDeclaration(path.parentPath);
     } else {
       path.parentPath.replaceWith(value);
@@ -32,18 +36,18 @@ export default function transpileNamespace(path, t, allowNamespaces) {
     path.replaceWith(value);
   } else {
     path.scope.registerDeclaration(
-      path.replaceWithMultiple([getDeclaration(t, name), value])[0],
+      path.replaceWithMultiple([getDeclaration(name), value])[0],
     );
   }
 }
 
-function getDeclaration(t, name) {
+function getDeclaration(name: string) {
   return t.variableDeclaration("let", [
     t.variableDeclarator(t.identifier(name)),
   ]);
 }
 
-function getMemberExpression(t, name, itemName) {
+function getMemberExpression(name: string, itemName: string) {
   return t.memberExpression(t.identifier(name), t.identifier(itemName));
 }
 
@@ -79,7 +83,7 @@ function handleVariableDeclaration(
     for (const declarator of declarations) {
       declarator.init = t.assignmentExpression(
         "=",
-        getMemberExpression(t, name, declarator.id.name),
+        getMemberExpression(name, declarator.id.name),
         declarator.init,
       );
     }
@@ -95,7 +99,7 @@ function handleVariableDeclaration(
     assignments.push(
       t.assignmentExpression(
         "=",
-        getMemberExpression(t, name, idName),
+        getMemberExpression(name, idName),
         t.cloneNode(bindingIdentifiers[idName]),
       ),
     );
@@ -113,9 +117,8 @@ function buildNestedAmbiendModuleError(path: NodePath, node: t.Node) {
 
 function handleNested(
   path: NodePath,
-  t: typeof import("@babel/types"),
   node: t.TSModuleDeclaration,
-  parentExport?,
+  parentExport?: t.Expression,
 ) {
   const names = new Set();
   const realName = node.id;
@@ -142,7 +145,7 @@ function handleNested(
           throw buildNestedAmbiendModuleError(path, subNode);
         }
 
-        const transformed = handleNested(path, t, subNode);
+        const transformed = handleNested(path, subNode);
         const moduleName = subNode.id.name;
         if (names.has(moduleName)) {
           namespaceTopLevel[i] = transformed;
@@ -151,7 +154,7 @@ function handleNested(
           namespaceTopLevel.splice(
             i++,
             1,
-            getDeclaration(t, moduleName),
+            getDeclaration(moduleName),
             transformed,
           );
         }
@@ -191,7 +194,7 @@ function handleNested(
           t.expressionStatement(
             t.assignmentExpression(
               "=",
-              getMemberExpression(t, name, itemName),
+              getMemberExpression(name, itemName),
               t.identifier(itemName),
             ),
           ),
@@ -215,7 +218,6 @@ function handleNested(
 
         const transformed = handleNested(
           path,
-          t,
           subNode.declaration,
           t.identifier(name),
         );
@@ -227,7 +229,7 @@ function handleNested(
           namespaceTopLevel.splice(
             i++,
             1,
-            getDeclaration(t, moduleName),
+            getDeclaration(moduleName),
             transformed,
           );
         }
diff --git a/packages/babel-preset-typescript/src/index.ts b/packages/babel-preset-typescript/src/index.ts
index e9fb7b515204..5fce63166f9e 100644
--- a/packages/babel-preset-typescript/src/index.ts
+++ b/packages/babel-preset-typescript/src/index.ts
@@ -18,7 +18,7 @@ export default declarePreset((api, opts: Options) => {
   } = normalizeOptions(opts);
 
   const pluginOptions = process.env.BABEL_8_BREAKING
-    ? (isTSX, disallowAmbiguousJSXLike) => ({
+    ? (isTSX: boolean, disallowAmbiguousJSXLike: boolean) => ({
         allowNamespaces,
         disallowAmbiguousJSXLike,
         isTSX,
@@ -27,7 +27,7 @@ export default declarePreset((api, opts: Options) => {
         onlyRemoveTypeImports,
         optimizeConstEnums,
       })
-    : (isTSX, disallowAmbiguousJSXLike) => ({
+    : (isTSX: boolean, disallowAmbiguousJSXLike: boolean) => ({
         allowDeclareFields: opts.allowDeclareFields,
         allowNamespaces,
         disallowAmbiguousJSXLike,
diff --git a/tsconfig.base.json b/tsconfig.base.json
index af2501b34cc3..64b95c92c311 100644
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -12,6 +12,7 @@
     "isolatedModules": true,
     "skipLibCheck": true,
     "resolveJsonModule": true,
-    "noImplicitThis": true
+    "noImplicitThis": true,
+    "noImplicitAny": true
   }
 }