Cú Roí (Cú Ruí, Cú Raoi) mac Dáire is a king of Munster in the Ulster Cycle of Irish mythology. He is usually portrayed as a warrior with superhuman abilities and a master of disguise possessed of magical powers. His name probably means "hound of the plain/field", or more specifically, "hound of the battlefield". He is the son of Dáire mac Dedad (or Dáire Doimthech), and thus belongs to the Clanna Dedad. However, T. F. O'Rahilly believed this to be artificial, stating that "Cú Roí and Dáire are ultimately one and the same".
Though often an outsider figure, for instance in the role of intervener or arbitrator, Cú Roí appears in a great number of medieval Irish texts, including Forfess Fer Fálgae, Amra Con Roi, Brinna Ferchertne, Aided Chon Roi (in several recensions), Fled Bricrenn, Mesca Ulad and Táin Bó Cúailnge. The early Irish tale-lists refer to such titles as Aided Chon Roí, Echtra Chon Roí (List A), Orgain Chathrach Chon Roí and Cathbúada Con Roí (List B), but only the first of these tales can be shown to have survived in some form. Several tales describe the enmity between him and the Ulster hero Cú Chulainn, who eventually kills him.
Read more about Cú Roí: Fled Bricrenn, Death Tale and Fragments, Clanna Dedad, Caherconree, Cú Roí in Welsh Literature