| Honorific Prefix: | His Grace |
| The Duke of Manchester | |
| Office: | Member of Parliament for Huntingdonshire |
| Term Start: | 1734 |
| Term End: | 1739 |
| Predecessor: | John Bigg Robert Piggott |
| Successor: | Robert Piggott Charles Clarke |
| Birth Name: | Robert Montagu |
| Party: | Whig |
| Parents: | Charles Montagu, 1st Duke of Manchester Dodington Greville |
| Children: | 4 |
| Relatives: | William Montagu, 2nd Duke of Manchester (brother) Charlotte Byng, Viscountess Torrington (sister) |
Robert Montagu, 3rd Duke of Manchester (– 10 May 1762) was a British politician who sat in the House of Commons from 1734 until 1739 when he succeeded to the peerage as Duke of Manchester.
Montagu was the son of Charles Montagu, 1st Duke of Manchester (1662–1721/2) and the former Hon. Dodington Greville (1671/2–1720/1). His elder brother was William Montagu, 2nd Duke of Manchester (who married Lady Isabella Montagu eldest daughter of John Montagu, 2nd Duke of Montagu and Lady Mary Churchill), Lady Charlotte Montagu (who married Pattee Byng, 2nd Viscount Torrington), and Lady Doddington Montagu.
His paternal grandparents were Robert Montagu, 3rd Earl of Manchester and the former Anne Yelverton (a daughter of Sir Christopher Yelverton, 1st Baronet). His maternal grandparents were Robert Greville, 4th Baron Brooke (son of Robert Greville, 2nd Baron Brooke) and the former Anne Dodington (daughter and heiress of John Doddington of Breamore, MP for Lymington). After his grandfather's death, his grandmother remarried to Thomas Hoby.
On 28 April 1719, his father, then the 4th Earl of Manchester, was created the Duke of Manchester by King George I. Upon his father's death, his elder brother succeeded as the 2nd Duke of Manchester.
Montagu was returned as a Whig MP for Huntingdonshire at the 1734 British general election. He vacated his seat when he succeeded his brother, who died without issue, to the peerage and the Manchester Duchy in 1739. From 1739 and 1762, he held the office of Lord-Lieutenant of Huntingdonshire.[1]
From 1735 to 1737, he served as Vice-Chamberlain to the Queen Consort. He was a Lord of the Bedchamber from 1739 to 1761,[2] and Lord Chamberlain to Queen Charlotte from 1761 until his death in 1762.[3]
On 3 April 1735, Montagu was married to Harriet Dunch, daughter and co-heiress of Edmund Dunch and his wife Elizabeth Godfrey, a noted beauty. She was a sister-in-law of Hugh Boscawen, 1st Viscount Falmouth and niece of John Churchill, 1st Duke of Marlborough. Together, Harriet and Robert were the parents of:[4] [5]
The 3rd Duke of Manchester died on 10 May 1762 leaving four children.[1]