Bricriu (also Briccriu, Bricne) is a hospitaller (briugu), troublemaker and poet in the Ulster Cycle of Irish mythology.
At the feast he promised the "champion's portion" to Cú Chulainn, then to Conall Cernach, then to Lóegaire Búadach, and the three heroes proceeded to compete for the honour.
(Two motifs in this story, the champion's portion and the beheading challenge, are mentioned by the Greek writer Posidonius as practices of the ancient Celts.
While he was a guest at Cruachan he caused a lot of trouble for Fergus and another lover of his, Flidais, which culminated at the Táin Bó Flidhais.
Later, Bricriu recovered but died at Cruachan at the end of the Táin Bó Cuailnge (Cattle Raid of Cooley), trampled to death by the two bulls as they fought.