William Donn de Burgh, 3rd Earl of Ulster

William Donn de Burgh (1312–1333), grandson of Richard Óg de Burgh, inherited the earldom of Ulster and was also lord of Connacht. He became Lieutenant of Ireland in 1331, and the next year had his cousin Walter Liath de Burgh starved to death at Greencastle.

Walter's kin took revenge: in 1333 they murdered William near Carrickfergus, led by Richard de Mandeville. His death plunged the de Burghs into the Burke Civil War. His infant daughter Elizabeth by Maud of Lancaster later married Lionel of Antwerp.