Ailill mac Fáeláin

Ailill mac Fáeláin was a King of Osraige in the south-east of Gaelic Ireland. Ailill was of the Dál Birn dynasty. Osraige was located in modern County Kilkenny, Ireland.

Ailill's year of accession is unknown, but it was after the reigns of both Cú Cherca mac Fáeláin, who died in 712, and Fland mac Congaile, whose reign is undated. The end of Ailill's reign is also unknown, but Cellach mac Fáelchair is recorded as king by 728.

Ailill is recorded in the king lists of the Book of Leinster, the synchronism's of Thurneysen, Boyle, and the Annals of Clonmacnoise. He is recorded as "Oillill" in the Annals of Clonmacnoise.

Ailill does not appear in the MS Rawlinson B 502 genealogies, but it is presumed that this Ailill was the son of Fáelán mac Crundmaíl (died 660) and the brother of Cú Cherca mac Fáeláin (died 712), who were both Kings of Osraige.