diff --git a/flat/flat.d.ts b/flat/flat.d.ts
new file mode 100644
index 000000000..f3698f125
--- /dev/null
+++ b/flat/flat.d.ts
@@ -0,0 +1,41 @@
+// Type definitions for flat
+// Project: https://github.com/hughsk/flat
+// Definitions by: Ilya Mochalov <https://github.com/chrootsu>
+// Definitions: https://github.com/borisyankov/DefinitelyTyped
+
+declare module FlatTypes {
+	interface FlattenOptions {
+		delimiter?: string;
+		safe?: boolean;
+		maxDepth?: number;
+	}
+
+	interface Flatten {
+		<TTarget, TResult>(
+			target: TTarget,
+			options?: FlattenOptions
+		): TResult;
+
+		flatten: Flatten;
+		unflatten: Unflatten;
+	}
+
+	interface UnflattenOptions {
+		delimiter?: string;
+		object?: boolean;
+		overwrite?: boolean;
+	}
+
+	interface Unflatten {
+		<TTarget, TResult>(
+			target: TTarget,
+			options?: UnflattenOptions
+		): TResult;
+	}
+}
+
+declare module "flat" {
+	var flatten: FlatTypes.Flatten;
+
+	export = flatten;
+}