Thomas de Courtenay, 5th/13th Earl of Devon was a nobleman from South West England. His seat was at Colcombe Castle near Colyton, and later at the principal historic family seat of Tiverton Castle, after his mother's death. The Courtenay family had historically been an important one in the region, and the dominant force in the counties of Devon and Cornwall. However, the rise in power and influence of several gentry families and other political players, in the years leading up to Thomas' accession to the earldom, threatened the traditional dominance of the earls of Devon in the area. Much of his life was spent in armed territorial struggle against his near-neighbour, Sir William Bonville of Shute, at a time when central control over the provinces was weak. This feud forms part of the breakdown in law and order in England that led to the Wars of the Roses.

Colcombe Castle was a castle or fortified house situated about a 0.5 mi (0.80 km) north of the town of Colyton in East Devon.