Theobald Bourke, 8th Mac William Iochtar (English: /bɜːrk/; BURK; died 1503) was an Irish chieftain and noble who succeeded his cousin (who retired in 1473) as lord of Lower (North) Connacht, Ireland. Theobald was the son of Walter mac Thomas de Búrca (Walter Bourke), 3rd Mac William Iochtar (d.1440). In 1473, he succeeded his cousin, Ricard Ó Cuairsge Bourke, 7th Mac William Íochtar (d. 1479) as chieftain. Theobald was succeeded by his brother, Ricard Bourke, 9th Mac William Íochtar (d.1509).