Sir Thomas de Brus (c. 1284 – 9 February 1307) was a younger brother of King Robert I of Scotland, who supported his brother in the struggle for the crown of Scotland. He was captured by forces at Loch Ryan, Galloway, Scotland and later executed as a traitor.
Born c. 1284 at Carrick, Ayrshire, Scotland a son of Robert de Brus, 6th Lord of Annandale and Margaret, Countess Of Carrick. He was married to Helen Erskine. While leading an invasion force with his brother Alexander de Brus composed of eighteen galleys, landing at Loch Ryan. The invasion force was quickly overwhelmed by local forces, led by Dungal MacDouall, who was a supporter of the Comyns and he and his brother were captured. He was later beheaded on 9 February 1307 in Carlisle, Cumberland, England.