Castlelyons is a small village in the east of County Cork, Ireland. It is also a civil parish in the barony of Barrymore. The name is derived from a stronghold of the Uí Liatháin - an early medieval kingdom. It is situated 6 km south of Fermoy. In the 2022 census the village recorded a population of 428. Castlelyons is part of the Dáil constituency of Cork East.