diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dffb14f..08d4e17 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,6 +38,9 @@ jobs:
       - name: Lint code
         run: npm run lint
 
+      - name: Check types
+        run: npm run test-types
+
       - name: Upload code coverage
         uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
         with:
diff --git a/.gitignore b/.gitignore
index f15b98e..282eaee 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,4 @@ coverage/
 node_modules/
 npm-debug.log
 package-lock.json
+*.lock
diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..b01689b
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,55 @@
+import type { IncomingMessage, ServerResponse } from 'node:http'
+import type {
+  Handler,
+  NextFunction,
+  RequestHandler,
+  Route as IRoute
+} from './lib/route'
+import Route = require('./lib/route')
+
+export type RouterMethod<T> = <F extends Handler = RequestHandler>(path: Path, handler: F) => T
+
+export type Path = string | RegExp | Array<string | RegExp>
+
+export interface RouterOptions {
+  caseSensitive?: boolean
+  mergeParams?: boolean
+  strict?: boolean
+}
+
+type MethodHandlers<T> = { [M in Method | 'all']: RouterMethod<T> }
+
+export interface Router extends RequestHandler, MethodHandlers<Router> {
+  params: Record<string, any>
+  stack: any[]
+  caseSensitive: boolean
+  mergeParams: boolean
+  strict: boolean
+
+  handle(req: IncomingMessage, res: ServerResponse, callback: NextFunction): void
+  param(name: string, fn: (req: any, res: any, next: NextFunction, value: any, name: string) => void): this
+  route(path: Path): IRoute
+
+  use: {
+   <F extends Handler = RequestHandler>(path: Path, handler: HandlerArg<F>, ...handlers: Array<HandlerArg<F>>): Router
+    <F extends Handler = RequestHandler>(handler: HandlerArg<F>, ...handlers: Array<HandlerArg<F>>): Router
+  }
+
+  all: RouterMethod<this>
+  get: RouterMethod<this>
+  post: RouterMethod<this>
+  put: RouterMethod<this>
+  delete: RouterMethod<this>
+  patch: RouterMethod<this>
+  options: RouterMethod<this>
+  head: RouterMethod<this>
+}
+
+interface RouterConstructor {
+  (options?: RouterOptions): Router
+  new (options?: RouterOptions): Router
+  Route: typeof Route
+}
+
+declare const router: RouterConstructor
+export = router
diff --git a/lib/route.d.ts b/lib/route.d.ts
new file mode 100644
index 0000000..56f6275
--- /dev/null
+++ b/lib/route.d.ts
@@ -0,0 +1,40 @@
+import type { IncomingMessage, ServerResponse } from 'node:http'
+
+export type NextFunction = (err?: any) => void
+
+export type RequestHandler = (req: IncomingMessage, res: ServerResponse, next: NextFunction) => void
+export type ErrorRequestHandler = (err: Error, req: IncomingMessage, res: ServerResponse, next: NextFunction) => void
+
+export type Handler = RequestHandler | ErrorRequestHandler
+
+export type HandlerArg<F extends Handler = Handler> = F | ReadonlyArray<HandlerArg<F>>
+
+export type RouteMethod<T> = <F extends Handler = RequestHandler>(handler: HandlerArg<F>, ...handlers: Array<HandlerArg<F>>) => T
+
+
+export type Method =
+  | 'acl' | 'bind' | 'checkout' | 'connect' | 'copy' | 'delete' | 'get'
+  | 'head' | 'link' | 'lock' | 'm-search' | 'merge' | 'mkactivity'
+  | 'mkcalendar' | 'mkcol' | 'move' | 'notify' | 'options' | 'patch'
+  | 'post' | 'propfind' | 'proppatch' | 'purge' | 'put' | 'query'
+  | 'rebind' | 'report' | 'search' | 'source' | 'subscribe' | 'trace'
+  | 'unbind' | 'unlink' | 'unlock' | 'unsubscribe'
+
+export type MethodHandlers<T> = { [M in Method | 'all']: RouteMethod<T> }
+
+export interface Route extends MethodHandlers<Route> {
+  path: string
+  stack: any[]
+  methods: Record<string, boolean>
+
+  _handlesMethod(method: string): boolean
+  _methods(): string[]
+  dispatch(req: IncomingMessage, res: ServerResponse, done: NextFunction): void
+}
+
+interface RouteConstructor {
+  new (path: Path): Route
+}
+
+declare const Route: RouteConstructor
+export = Route
diff --git a/package.json b/package.json
index e6be557..a75c80b 100644
--- a/package.json
+++ b/package.json
@@ -8,6 +8,9 @@
   ],
   "license": "MIT",
   "repository": "pillarjs/router",
+  "type": "commonjs",
+  "main": "index.js",
+  "types": "index.d.ts",
   "funding": {
     "type": "opencollective",
     "url": "https://opencollective.com/express"
@@ -20,7 +23,11 @@
     "path-to-regexp": "^8.0.0"
   },
   "devDependencies": {
+    "@arethetypeswrong/cli": "0.18.5",
+    "@tsconfig/node18": "18.2.6",
+    "@types/node": "18.19.130",
     "finalhandler": "^2.1.0",
+    "expect-type": "1.4.0",
     "mocha": "10.2.0",
     "nyc": "15.1.0",
     "run-series": "^1.1.9",
@@ -32,7 +39,8 @@
     "LICENSE",
     "HISTORY.md",
     "README.md",
-    "index.js"
+    "index.js",
+    "index.d.ts"
   ],
   "engines": {
     "node": ">= 18"
@@ -43,6 +51,7 @@
     "test:debug": "mocha --reporter spec --check-leaks test/ --inspect --inspect-brk",
     "test-ci": "nyc --reporter=lcov --reporter=text npm test",
     "test-cov": "nyc --reporter=text npm test",
-    "version": "node scripts/version-history.js && git add HISTORY.md"
+    "version": "node scripts/version-history.js && git add HISTORY.md",
+    "test-types": "tsc --noEmit && attw --pack"
   }
 }
diff --git a/test/types.ts b/test/types.ts
new file mode 100644
index 0000000..9eb3c3b
--- /dev/null
+++ b/test/types.ts
@@ -0,0 +1,118 @@
+import { IncomingMessage, ServerResponse } from "node:http";
+import { expectTypeOf } from "expect-type";
+import Router, { ErrorRequestHandler, Method, NextFunction, Path, RequestHandler } from "..";
+
+const router = Router();
+
+const handler: RequestHandler = (req, res, next) => next();
+const other: RequestHandler = (req, res, next) => next();
+
+// handler parameters are inferred
+router.get("/", function (req, res) {
+  expectTypeOf(req).toEqualTypeOf<IncomingMessage>();
+  expectTypeOf(res).toEqualTypeOf<ServerResponse>();
+});
+
+router.get("/", function (req, res, next) {
+  expectTypeOf(req).toEqualTypeOf<IncomingMessage>();
+  expectTypeOf(res).toEqualTypeOf<ServerResponse>();
+  expectTypeOf(next).toBeFunction();
+});
+
+// typescript has no way to infer the types automatically
+router.get<ErrorRequestHandler>("/", function (err, req, res, next) {
+  expectTypeOf(err).toEqualTypeOf<Error>();
+  expectTypeOf(req).toEqualTypeOf<IncomingMessage>();
+  expectTypeOf(res).toEqualTypeOf<ServerResponse>();
+  expectTypeOf(next).toBeFunction();
+});
+
+// methods accept multiple handlers and nested arrays (flattened at runtime)
+router.get("/", handler, other);
+router.get("/", [handler, other]);
+router.get("/", [handler, [other]], handler);
+
+// at least one handler is required (runtime throws TypeError)
+// @ts-expect-error
+router.get("/");
+// handlers must be functions or arrays of them
+// @ts-expect-error
+router.get("/", "not-a-handler");
+
+// paths may be a string, RegExp, or array of either
+router.get(/^\/x/, handler);
+router.get(["/a", /^\/b/], handler);
+// @ts-expect-error
+router.get(42, handler);
+
+// use: with or without path, multiple handlers, arrays
+router.use(handler);
+router.use(handler, other);
+router.use([handler, [other]]);
+router.use("/a", handler, [other], handler);
+router.use(["/a", "/b"], handler);
+router.use(/^\/c/, handler);
+// @ts-expect-error path without any handler (runtime throws TypeError)
+router.use("/x");
+// @ts-expect-error
+router.use();
+
+// verb methods and use return the router for chaining
+expectTypeOf(router.get("/", handler)).toEqualTypeOf(router);
+router.use(handler).use("/a", other).get("/", handler);
+
+// one method per node:http METHODS entry, not just the classic 8
+router.trace("/", handler);
+router.search("/", handler);
+router.propfind("/", handler);
+router["m-search"]("/", handler);
+// @ts-expect-error not an HTTP method
+router.foo("/", handler);
+
+// error handlers are distinguished by the explicit generic
+router.use<ErrorRequestHandler>(function (err, req, res, next) {
+  expectTypeOf(err).toEqualTypeOf<Error>();
+  next(err);
+});
+
+// param callbacks receive typed req/res
+router.param("id", function (req, res, next, value, name) {
+  expectTypeOf(req).toEqualTypeOf<IncomingMessage>();
+  expectTypeOf(res).toEqualTypeOf<ServerResponse>();
+  expectTypeOf(next).toEqualTypeOf<NextFunction>();
+  expectTypeOf(name).toBeString();
+});
+
+// router is itself a request handler (mountable in a server or another router)
+expectTypeOf(router).toExtend<RequestHandler>();
+router.use(Router());
+
+// the instance, options, and helper types are nameable by consumers
+const mounted: Router.Router = Router({ strict: true, caseSensitive: true, mergeParams: true });
+mounted.use(handler);
+const opts: Router.RouterOptions = { strict: true };
+Router(opts);
+new Router(opts);
+// @ts-expect-error unknown options are rejected
+Router({ nope: true });
+expectTypeOf<Method>().toExtend<string>();
+expectTypeOf<Path>().toEqualTypeOf<string | RegExp | Array<string | RegExp>>();
+
+// routes: all verbs, multiple handlers, chaining
+const route = router.route("/things/:id");
+expectTypeOf(route.path).toBeString();
+route.all(handler).get(handler, other).post([handler, [other]]);
+route.checkout(handler);
+route["m-search"](handler);
+// @ts-expect-error at least one handler is required
+route.put();
+
+// Route must be constructed with new, and accepts any Path
+new Router.Route("/x");
+new Router.Route(/^\/x/);
+new Router.Route(["/a", /^\/b/]);
+// @ts-expect-error calling without new does not construct (strict mode)
+Router.Route("/x");
+// @ts-expect-error
+new Router.Route(42);
+
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..369ea4e
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "extends": "@tsconfig/node18/tsconfig.json",
+  "include": ["index.d.ts", "lib/route.d.ts", "test/types.ts"],
+  "compilerOptions": {
+    "types": ["node"]
+  }
+}