Castlerea is the third largest town in County Roscommon, Ireland. It is located in the west of the county and had a population of 1,992 at the 2016 census. Roughly translated from Irish, Castlerea is generally thought to mean 'brindled castle'. An alternative translation is 'castle of the king'. The town is built on the banks of the River Suck and the River Francis, both of which are tributaries of the River Shannon.

County Roscommon is a county in Ireland. It is part of the province of Connacht and the Northern and Western Region. It is the 11th largest Irish county by area and 26th most populous. Its county town and largest town is Roscommon. Roscommon County Council is the local authority for the county. The population of the county was 69,995 as of the 2022 census.