Ailill mac Fáeláin

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

Ailill was a "Reges Ossairge", a King of Osraige, his year of accession is unknown, however, it was after both the reign of Cú Cherca mac Fáeláin, who had died in 712, and Fland mac Congaile who is without a date. The end of his reign is also unknown, however, by 728 Cellach mac Fáelchair had been recorded King.

Ailill is recorded in the Book of Leinster's king lists, and the synchronism's of Thurneysen, Boyle, as well as 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 King's of Osraige.