The Déisi were a social class in Ireland between the ancient and early medieval period. The various peoples listed under the heading déis shared a similar status in Gaelic Ireland, and had little or no actual kinship, though they were often thought of as genetically related. During the era of Roman rule in Britain, many members of the Déisi were recorded as settling in western coastal areas.

Munster is one of the four provinces of Ireland, located in the south of the island. In early Ireland, the Kingdom of Munster was one of the kingdoms of Gaelic Ireland ruled by a "king of over-kings". Following the Norman invasion of Ireland, the ancient kingdoms were shired into counties for administrative and judicial purposes. In later centuries, local government legislation has seen further sub-division of the historic counties.