William O. Tiron. (died early 1290s) was a late 13th-century Tironensian abbot and bishop in the Kingdom of Scotland. He appears in the extant sources for the first time on 25 April 1276; he is Abbot of Arbroath. According to the Scotichronicon, the work of the 15th-century historian Walter Bower, William's predecessor Adam de Inverlunan had died in 1275, so William probably became abbot in either that year or in 1276.