Muireadhach Ua Flaithbheartaigh (died 1121) was King of Iar Connacht.
According to the Annals of the Four Masters, sub anno 1121:
<blockquote> A hosting by Toirdhealbhach, son of Ruaidhràinto Munster, and he burned Ciarraighe Luachra and went from there eastwards through Munster, and burned Ua Caoimh's house on the bank of the Abha Mhór, and his scouts came to Magh Ceithniuil and Druim FÃÂnghin. On that day were killed Muireadhach Ua Flaithbheartaigh, king of Iarthar Connacht, and Aodh Ua hEidhin, king of UàFhiachrach Aidhne, to avenge the profanation of Mo-Chuda, although Toirdhealbhach made compensation for the plundering. An encampment by Toirdhealbhach, son of RuaidhrÃÂ, at Magh Biorra during the winter, and he made a settlement between Clann Charthaigh and SÃÂol Briain, and they both submitted to him. </blockquote>