O'Connor (Ó Conchobair), Fedlimid (1293–1316), king of Connacht, was son of Áed mac Eógain O'Connor (qv) (c.1265–1309), king of Connacht, and of a daughter of Geoffrey O'Farrell (Séfraid Ó Fergail) of Anghaile. In 1293 Áed mac Eógain, with the help of the justiciar, William de Vescy (qv), claimed the provincial kingship after the death of King Magnus O'Connor. Áed mac Eógain fostered Fedlimid in the house of Máelruanaid MacDermot (qv) (d. 1331), king of Moylurg and traditional inaugurator of the O'Connor kings of Connacht. There Fedlimid spent his boyhood and youth, while his father battled for survival against his rivals, the O'Connors of Clann Muirchertaig Muimnig. In 1309 Áed mac Eógain was killed by his rivals after attacking their territory in Breifne. When Áed Bréifnech O'Connor (qv), leader of the Clann Muirchertaig Muimnig, attempted to claim the Connacht kingship, MacDermot sprang to Fedlimid's defence, gathered a force of both English and Irish nobles, and defended Fedlimid's rights to succeed his father, resulting in Áed Bréifnech's devastation of Moylurg during the next year. When the Burkes then assassinated Áed Bréifnech, the situation worsened for Fedlimid. The Burkes began to billet troops throughout Connacht, threatening the remaining independence of the O'Connor kingship. When MacDermot saw that Fedlimid's rights were being ignored, he as leading vassal took it on himself to defend the Connacht kingship. Consequently, sometime during 1310 he took Fedlimid to Carnfree, and amid great festivities inaugurated him according to ancient rites.
However, Fedlimid's grip on the Connacht kingship was insecure and under threat from Áed Bréifnech's brother, Ruaidrí O'Connor (qv). To counter the landing of Edward Bruce (qv) in Ulster during May 1315, Richard de Burgh (qv), earl of Ulster and lord of Connacht, marched with Fedlimid from Connacht to confront him. Unknown to the earl, Bruce's envoys tempted Fedlimid to take his side, and finding him receptive they returned to their master. In fact, Bruce also promised the crown to Ruaidrí, provided he did not attack Fedlimid. After this, Ruaidrí burned the country from Sligo to Athlone. At the height of the disturbances Ruaidrí went to MacDermot and asked him to inaugurate him as provincial king, but was refused. This, however, did not prevent Ruaidrí from making himself king at Carnfree. On hearing of Ruaidrí's activities, Fedlimid made his excuses to the earl, returned to Connacht, and met with his uncle Seaán O'Farrell and MacDermot. However, Ruaidrí was dominant. When Burke returned to Connacht after his defeat by Bruce at Connor (September 1315), Fedlimid and his nobles sought his protection. According to the annals, MacDermot felt ashamed by the sight of the Connacht nobility pandering to Burke, and as a result he decided to seek terms with Ruaidrí.
But MacDermot's abandonment of Fedlimid was brief, as he rescued him from the clutches of Ruaidrí's supporters towards the end of 1315. Moreover, the return of MacDermot to Fedlimid's fold may have led to a more aggressive stance by Fedlimid in 1316. In the new year they seem to have adopted a new strategy: first, to defeat and kill Ruaidrí, and secondly to reverse the English colonisation of Connacht. The first objective was gained with the aid of the English of Connacht at Templetogher, Co. Galway (24 February 1316). Thereafter Fedlimid cut loose, taking hostages from the Connacht nobility and setting up a king over Breifne. His boldness and the seeming Burke weakness triggered an uprising of the Irish of Meath, Offaly, Thomond, and Connacht, and allowed Fedlimid to fashion an army intent on expelling the English from Connacht. This resulted in wide-ranging attacks on English settlements throughout the province, as well as the burning of the royal castles of Roscommon, Rindown, and Athlone. However, the return of William de Burgh (qv) to Connacht from captivity in Scotland stiffened the resistance of the settlers. Outside Athenry (10 August) he routed Fedlimid's army, killing the king. Fedlimid was succeeded by his cousin, Ruaidrí O'Connor of the Faes.