MONTAGU, RALPH, 1st Duke of (c. 1638—1709), English diplomatist, was the second son of Edward, 2nd Baron Montagu of Boughton (1616–1684), whose peerage was one of several granted in the 17th century to different members of the Montagu family (q.v.). Sir Edward Montagu, chief justice of the king’s bench in the time of Henry VIII., was grandfather of the first earl of Manchester (see Manchester, Earls and Dukes of), and of Edward, 1st Baron Montagu of Boughton (1562–1644), who was imprisoned in the Tower by the parliament on account of his loyalty to Charles I. The eldest son of the latter, Edward, who succeeded him as 2nd baron, took the side of the parliament in the Civil War, and was one of the lords who conducted the king from Newark to Holmby House after his surrender by the Scots in January 1647. He had two sons, of whom Ralph was the younger. The eldest son, Edward, was master of the horse to Queen Catherine, wife of Charles II., a post from which he is said to have been dismissed by the king for showing attention to the queen of too ardent a nature. Catherine immediately appointed the younger brother, Ralph, to the vacant situation, and the latter soon acquired a reputation for gallantry at the court of Charles II. He took an active part in the negotiations in which Louis XIV. purchased the neutrality of England in the war between France and Holland. Having quarrelled with Danby and the duchess of Cleveland, who denounced him to the king, Montagu was elected member of parliament for Northampton in 1678, with the intention of bringing about the fall of Danby; but, having produced letters seriously compromising the minister, the dissolution of parliament placed him in such danger of arrest that he attempted to fly to France. Foiled in this design, he continued to intrigue against the government, supporting the movement for excluding the duke of York from the succession and for recognizing Monmouth as heir to the crown. His elder brother having predeceased his father, Ralph became Baron Montagu of Boughton on the death of the latter in 1684. Notwithstanding his former intrigues he gained the favour of James II. on his accession to the throne; but this did not deter him from welcoming William of Orange, who created him Viscount Monthermer and earl of Montagu in 1689. Montagu was no less avaricious than unscrupulous. In 1673 he had married the wealthy widow of the earl of Northumberland, Elizabeth Wriothesley, daughter of the earl of Southampton, who brought him a large fortune; and after her death in 1690 he married the still more wealthy Elizabeth Cavendish, daughter of the duke of Newcastle, and widow of Christopher Monk, 2nd duke of Albemarle. Montagu’s position was further strengthened in 1705 by the marriage of his son and heir to Mary, daughter of the great duke of Marlborough. In the same year he was raised to the dukedom as duke of Montagu and marquess of Monthermer. He died on the 9th of March 1709. His London residence, Montagu House, Bloomsbury, was bought by the government in 1753 to hold the national collection of antiquities, and on its site was built the British Museum.
The duke was succeeded by his son John, 2nd duke of Montagu (1689–1749), who in 1745 raised a cavalry regiment known as Montagu’s Carabineers, which, however, was disbanded after Culloden. He was made a K.G. in 1719, and was a fellow of the Royal Society. As neither of his two sons survived him the title became extinct at his death in 1749, but in 1730 his daughter Mary married George Brudenell, 4th earl of Cardigan (1712–1790), who on his father-in-law’s death assumed the name and arms of Montagu, and in 1766 was created duke of Montagu. On his death, in 1790, this second dukedom of Montagu also became extinct; his only son, who was created Baron Montagu of Boughton, having predeceased him. His daughter Elizabeth married Henry, 2nd duke of Buccleuch, who thus acquired all the unentailed property of the dukes of Montagu, the entailed portion passing to the earls of Cardigan. See Abel Boyer, History of the Reign of Queen Anne, vol. viii. (11 vols., London, 1703–1713); Sir J. B. Burke, Genealogical History of Dormant (&c.) Peerages (London, 1883).