In the Ulster Cycle of Irish mythology, Finnbhennach ("white-horned") was an extremely fertile stud bull owned by king Ailill of Connacht. Wikipedia does not yet have an article with this exact name. ... The mythology of pre-Christian Ireland did not entirely survive the conversion to Christianity, but much of it was preserved, shorn of its religious meanings, in medieval Irish literature, which represents the most extensive and best preserved of all the branches of Celtic mythology. ... Ailill (Aillell, Oilioll) mac Máta was king of Connacht and husband of Medb in the Ulster Cycle of Irish mythology. ... Connaught redirects here. ...

He was originally one of Bodb Dearg's pig-keepers, who fell out with one of his colleagues. The two fought, taking a series of animal and human forms, before finally becoming two worms who were swallowed by two cows and reborn as two bulls, Finnbhennach and Donn Cuailnge. Finnbhennach was born into the herds of queen Medb, but thought belonging to a woman beneath him and joined her husband's herds instead. In Irish mythology, Bodb Dearg mac an Daghda (Bodb the Red) was a son of the Dagda and succeeded him as King of the Tuatha De Danaan. ... In the Ulster Cycle of Irish mythology Donn Cuailnge, the Brown Bull of Cooley, was an extremely fertile stud bull over whom the Táin Bó Cuailnge (Cattle Raid of Cooley) was fought. ... (, Medb, Medhbh, Meabh, Maeve, Maev) is queen of Connacht in the Ulster Cycle of Irish mythology. ...

Donn Cuailnge was born into the herds of Dáire mac Fiachna of Cooley. He bulled a heifer belonging to the Mórrígan, and the resulting bull-calf fought Finnbhennach, and narrowly lost. After seeing that Medb was determined to see Finnbhennach fight the bull-calf's sire.

When Medb discovered that owning Finnbhennach made Ailill richer than her, she resolved to even the account by possessing Donn Cuailnge. She launched the Táin Bó Cuailnge (Cattle Raid of Cooley) and eventually brought Donn back to Cruachan. The two bulls fought. Finnbhennach was killed, Donn Cuailnge mortally wounded. The Táin Bó Cúailnge, or Cattle Raid of Cooley, is the central tale in the Ulster Cycle, one of the four great cycles that make up the surviving corpus of Irish mythology. ...