The title of Duke of Montagu has been created several times. It was first created in the Peerage of England in 1705 for Ralph Montagu, with the subsidiary title Marquess of Montagu, but became extinct in 1749. It was then recreated in the Peerage of Great Britain in 1766 for George Montagu, 4th Earl of Cardigan, with the subsidiary title Marquess of Monthermer. On his death in 1790 the dukedom and marquessate became extinct, and the earldom passed to his brother, James Brudenell, 5th Earl of Cardigan.