diff --git a/types/y18n/index.d.ts b/types/y18n/index.d.ts
new file mode 100644
index 0000000000..ccb02382bf
--- /dev/null
+++ b/types/y18n/index.d.ts
@@ -0,0 +1,60 @@
+// Type definitions for y18n 4.0
+// Project: https://github.com/yargs/y18n
+// Definitions by:  Adam Zerella <https://github.com/adamzerella>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 2.2
+
+interface Config {
+    /**
+     * The locale directory, default ./locales.
+     */
+    directory: string;
+    /**
+     * Should newly observed strings be updated in file, default true.
+     */
+    updateFiles: boolean;
+    /**
+     * What locale should be used.
+     */
+    locale: string;
+    /**
+     * Should fallback to a language-only file (e.g. en.json) be allowed
+     * if a file matching the locale does not exist (e.g. en_US.json), default true.
+     */
+    fallbackToLanguage: boolean;
+}
+
+declare class Y18N {
+    /**
+     * Create an instance of y18n with the config provided
+     */
+    constructor(config?: Config)
+
+    /**
+     * Print a localized string, %s will be replaced with args.
+     */
+    __(str: string, arg1?: string, arg2?: string, arg3?: string): string;
+
+    /**
+     * Print a localized string with appropriate pluralization.
+     * If %d is provided in the string, the count will replace this placeholder.
+     */
+    __n(singularString: string, pluralString: string, count: number, arg1?: string, arg2?: string, arg3?: string): string;
+
+    /**
+     * Set the current locale being used.
+     */
+    setLocale(str: string): void;
+
+    /**
+     * What locale is currently being used?
+     */
+    getLocale(): string;
+
+    /**
+     * Update the current locale with the key value pairs in obj.
+     */
+    updateLocale(obj: object): void;
+}
+
+export = Y18N;
diff --git a/types/y18n/tsconfig.json b/types/y18n/tsconfig.json
new file mode 100644
index 0000000000..632e88a450
--- /dev/null
+++ b/types/y18n/tsconfig.json
@@ -0,0 +1,25 @@
+{
+    "compilerOptions": {
+      "module": "commonjs",
+      "lib": [
+        "es6"
+      ],
+      "noImplicitAny": true,
+      "noImplicitThis": true,
+      "strictNullChecks": true,
+      "strictFunctionTypes": true,
+      "baseUrl": "../",
+      "typeRoots": [
+        "../"
+      ],
+      "types": [
+
+      ],
+      "noEmit": true,
+      "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+      "index.d.ts",
+      "y18n-tests.ts"
+    ]
+}
diff --git a/types/y18n/tslint.json b/types/y18n/tslint.json
new file mode 100644
index 0000000000..e60c15844f
--- /dev/null
+++ b/types/y18n/tslint.json
@@ -0,0 +1,3 @@
+{
+    "extends": "dtslint/dt.json"
+}
\ No newline at end of file
diff --git a/types/y18n/y18n-tests.ts b/types/y18n/y18n-tests.ts
new file mode 100644
index 0000000000..39bfd63360
--- /dev/null
+++ b/types/y18n/y18n-tests.ts
@@ -0,0 +1,21 @@
+import y18n = require("y18n");
+
+// Testing custom config
+new y18n({
+    directory: '../locales',
+    updateFiles: false,
+    locale: 'en-AU',
+    fallbackToLanguage: false
+});
+
+const Y18N = new y18n();
+
+Y18N.__(`my awesome string: foo`);
+
+Y18N.__n('one fish %s', '%d fishes %s', 2, 'foo');
+
+Y18N.setLocale('en-US');
+
+Y18N.getLocale();
+
+Y18N.updateLocale({});