Erris is a barony in northwestern County Mayo in Ireland consisting of over 230,452 acres (932.61 km2), much of which is mountainous blanket bog. It has extensive sea coasts along its west and north boundaries. The main towns are Belmullet and Bangor Erris. The name Erris derives from the Irish 'Iar Ros' meaning 'western promontory'. The full name is the Iorrais Domnann, after the Fir Bolg tribe, the Fir Domnann. To its north is the wild Atlantic Ocean and the bays of Broadhaven and Sruth Fada Conn and to its west is Blacksod Bay. Its main promontories are the Doohoma Peninsula, Mullet Peninsula, Erris Head, the Dún Chiortáin and Dún Chaocháin peninsulas and Benwee Head.

Blacksod Bay is a bay of the Atlantic Ocean in Erris, north County Mayo, Ireland. The 16 km (9.9 mi) long and 8 km (5.0 mi) wide bay is bounded on its western side by the Mullet Peninsula. Its eastern side includes Kiltane Parish, which extends southwards from Belmullet towards Gweesalia and Doohoma.