Founder of the English Branch of the House of Courtenay.

Reginald de Courtenay's grandson, Robert de Courtenay (d.1242), feudal baron of Okehampton, Devon (in right of his mother Hawise de Curcy (d.1219),) married Mary de Redvers, daughter and heiress of William de Redvers, 5th Earl of Devon (d.1217), seated at Tiverton Castle and Plympton Castle in Devon. On the death of Isabel de Forz, suo jure 8th Countess of Devon in 1293 (the sister and heiress of Baldwin de Redvers, 7th Earl of Devon (1236-1262)) she was succeeded by her cousin Hugh de Courtenay, 1st/9th Earl of Devon (d.1340), feudal baron of Okehampton, the great-grandson of Robert de Courtenay (d.1242).

His title of Earl of Devon was not however officially recognised until 1335, and it remains unclear whether it was a new creation or a continuation of the Redvers title, with different modern sources giving him as either 1st or 9th Earl of Devon. The senior line seated at Tiverton, Okehampton and Plympton, died out in 1471 during the Wars of the Roses, but the Earldom was recreated three more times in 1485, 1511 and 1553 for cousins, all descended from the eldest son of the 2nd/10th Earl. William Courtenay, 1st Earl of Devon (1475-1511), would marry Princess Catherine of the Royal House of York, a younger daughter of King Edward IV, bringing the Earls of Devon very close to the line of succession to the English throne.

On the death of Edward Courtenay, 1st Earl of Devon (1527-1556), unmarried at Padua in 1556, the subject of the final creation of 1553, the title was considered extinct until declared in 1831 by the House of Lords to have been merely dormant, when it was confirmed to William Courtenay, Viscount Courtenay (1768-1835) (of the surviving junior line seated at Powderham Castle in Devon, descended from the fourth son of the 2nd/10th Earl) who became the 9th Earl of Devon. The family survives in the male line and is headed by Charles Courtenay, 19th Earl of Devon, of Powderham.