Ainbíth mac Áedo was a Dál Fiatach king of Ulaid. He was the grandson of Eochaid mac Fiachnai (died 810), a previous king of Ulaid. He ruled from 873-882. He was the son of Aodha mac Eochaid, who was not a king, but moved the Dál Fiatach north by building Lois Aedha I. Ainbíth built Lois Aedha II.
Ainbíth became king in 873 and in 878 the Ulaid killed Cummascach mac Muiredaig, King of the Uá Cremthainn (a tribe of the Airgialla in County Fermanagh and County Monaghan). In 882 the Ualid fought a skirmish with the Conaille Muirtheimne of County Louth. Ainbíth was slain along with his ally Conallán mac Máele Dúin, king of the Uí Echach Cobo of west County Down.