Flaithbertach mac Inmainén

Flaithbertach mac Inmainén (died 944) was abbot of Inis Cathaig (Scattery Island) and sometime King of Munster in the south of Ireland. Unrelated to the dominant Eóganachta, Flaithbertach belonged to the Múscraige, an Érainn people.

Flaithbertach is first mentioned by the Irish annals in 907, when he is recorded, along with the then-King of Munster Cormac mac Cuilennáin, leading an expedition by the Munstermen against Connacht and the Uí Néill. According to the partisan pro-Munster Annals of Innisfallen, Cormac and Flaithbertach defeated Flann Sinna, the High King of Ireland, and later obtained hostages from the Uí Néill. The northern Annals of Ulster make no mention of this although the late Annals of the Four Masters agree with the Annals of Innisfallen.

In 908 Cormac and Flaithbertach collected an army to campaign against their eastern neighbours, Leinster, whose king Cerball mac Muirecáin was Flann Sinna's son-in-law and staunch ally. The Fragmentary Annals of Ireland, a source compiled in the 11th century for Donnchad mac Gilla Pátraic, king of Osraige and king of Leinster, contain a long account of this campaign, perhaps written within living memory.