The title of Duke of Montagu has been created twice for members of the noble House of Montagu. It was first created in the Peerage of England in 1705 for Ralph Montagu, 3rd Baron Montagu of Boughton, with the subsidiary title Marquess of Monthermer, but became extinct in 1749. The first Duke had been created Earl of Montagu and Viscount Monthermer in 1689. The Dukedom was then recreated in the Peerage of Great Britain in 1766 for the late Duke's son-in-law, George Montagu (né Brudenell), 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. The dukedom is named for the ancient Anglo-Norman family rather than any place.
Earls of Montagu (1689)
- Other titles: Baron Montagu of Boughton (1621)
- Ralph Montagu, 3rd Baron Montagu of Boughton, 1st Earl of Montagu (1638–c. 1709) (created Duke of Montagu in 1705)
Dukes of Montagu, first Creation (1705)
- Other titles: Earl of Montagu (1621) and Baron Montagu of Boughton (1621)
- Ralph Montagu, 1st Duke of Montagu (1638–c. 1709) was a courtier and diplomat
- John Montagu, 2nd Duke of Montagu (1690–1749), only son of the 1st Duke, died without male issue
Dukes of Montagu, second Creation (1766)
- Other titles: Marquess of Monthermer (1766), Earl of Cardigan (1661), Baron Brudenell of Stonton, in the county of Leicester (1628) and Baron Montagu of Boughton, in the county Northampton (1786)
- George Montagu, 1st Duke of Montagu (1712–1790), son-in-law of the late 2nd Duke
- John Montagu, Marquess of Monthermer (1735–1770), only son of the 1st Duke, predeceased his father unmarried
Family tree
| Sir Edward Montagu, L.C.J. (c.1485–1557) | |||||||||||||||||||||||||||||||||||||||||||
| Sir Edward Montagu (c.1530–1602) | |||||||||||||||||||||||||||||||||||||||||||
| BARON MONTAGU of Boughton, 1621 | Earls of Sandwich | ||||||||||||||||||||||||||||||||||||||||||
| Edward, 1st Lord Montagu of Boughton (1563–1644) | Sir Henry Montagu, 1st Earl of Manchester (c.1563–1642) | ||||||||||||||||||||||||||||||||||||||||||
| Earls of Halifax | |||||||||||||||||||||||||||||||||||||||||||
| Edward, 2nd Lord Montagu of Boughton (1616–1684) | Edward Montagu, 2nd Earl of Manchester (1602–1671) | ||||||||||||||||||||||||||||||||||||||||||
| EARL OF MONTAGU, 1689 DUKE OF MONTAGU, 1705 | |||||||||||||||||||||||||||||||||||||||||||
| Edward Montagu (c.1636–1665) | Robert Montagu, 3rd Earl of Manchester (1634–1683) | Ralph, 3rd Lord Montagu, 1st Earl of Montagu, 1st Duke of Montagu (1638–1709) | |||||||||||||||||||||||||||||||||||||||||
| Charles Montagu, , 4th Earl of Manchester, 1st Duke of Manchester (c. 1662 – 1722) | John Montagu, 2nd Duke of Montagu (1690–1749) | ||||||||||||||||||||||||||||||||||||||||||
| DUKE OF MONTAGU, 1766 | |||||||||||||||||||||||||||||||||||||||||||
| (1) William Montagu, 2nd Duke of Manchester (1700–1739) | Lady Isabella Montagu (d.1786) m2. 1st Earl Beaulieu | Lady Mary Montagu (c.1711–1785) | George Brudenell (Montagu), 4th Earl of Cardigan, 1st Duke of Montagu (1712–1790) | ||||||||||||||||||||||||||||||||||||||||
| childless | |||||||||||||||||||||||||||||||||||||||||||
| two children, but both died without issue | BARON MONTAGU of Boughton, 1762 | ||||||||||||||||||||||||||||||||||||||||||
| John Brudenell (Montagu), Marquess of Monthermer, 1st Baron Montagu (1735–1770) | Lady Elizabeth Montagu (1743–1827) m. 3rd Duke of Buccleuch | ||||||||||||||||||||||||||||||||||||||||||