Ailill Caisfiaclach ("having crooked/hateful teeth"), son of Connla Cáem, was, according to medieval Irish legends and historical traditions, a High King of Ireland. He succeeded his father, and reigned for twenty-five years, until he was killed by Adamair, the son of the man who had killed Ailill's grandfather. The Lebor Gabála Érenn synchronises his reign with that of Ptolemy V Epiphanes in Egypt (204–181 BC). Geoffrey Keating's Foras Feasa ar Éirinn dates his reign from 315 to 290 BC, the Annals of the Four Masters from 443 to 418 BC.