diff --git a/username/username-tests.ts b/username/username-tests.ts
new file mode 100644
index 000000000..46265958b
--- /dev/null
+++ b/username/username-tests.ts
@@ -0,0 +1,10 @@
+/// <reference path="./username.d.ts" />
+
+import username = require("username");
+
+username(function(err, username) {
+    err === new Error();
+    username === "string";
+});
+
+username.sync() === "string";
diff --git a/username/username.d.ts b/username/username.d.ts
new file mode 100644
index 000000000..5784f46ff
--- /dev/null
+++ b/username/username.d.ts
@@ -0,0 +1,27 @@
+// Type definitions for username v1.0.1
+// Project: https://www.npmjs.com/package/username
+// Definitions by: Klaus Reimer <https://github.com/kayahr>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+declare module "username" {
+    /**
+     * Tries to get the username from the LOGNAME, USER, LNAME or USERNAME environment variables.
+     * Falls back to `id -un` on OS X / Linux and `whoami` on Windows in the rare case none of the environment 
+     * variables are set. The result is cached.
+     *
+     * @param callback The callback function to call asynchronously with the result.
+     */
+    function username(callback: (err: Error, result: string) => void): void;
+    
+    module username {
+        /**
+         * Tries to get the username from the LOGNAME, USER, LNAME or USERNAME environment variables. Falls back
+         * to returning an empty string in the reare case none of the environment variables are set.
+         *
+         * @return The username or empty string if not found.
+         */
+        function sync(): string;
+    }
+
+    export = username;
+}