Ayn may refer to:
- Ayin or ʿayn, a letter in many Semitic scripts
- Ayn, Savoie, a commune of the Savoie département' of France
- Ayn, Somalia (or Cayn), a region defined by the autonomous state of Puntland
- Ghayn (Ғ,ғ), a letter used in the Kazakh, Uzbek, and Azerbaijani alphabets
- Ayn Rand, Russian-born American novelist and philosopher