| Robert Hampden-Trevor | |
| Office1: | Postmaster General of the United Kingdom |
| Term1: | 1759-1765 |
| Alongside1: | The Earl of Bessborough (1759-1762) The Earl of Egmont (1762–1763) The Lord Hyde (1763–1765) |
| Term2: | 1739–1746 |
| Birth Date: | 17 February 1706 |
| Education: | The Queen's College, Oxford |
| Parents: | Thomas Trevor and Anne Trevor |
| Children: | 2+, including John |
Robert Hampden-Trevor, 1st Viscount Hampden (17 February 1706 – 22 August 1783) was a British diplomat at The Hague and then joint Postmaster General.
He was the eldest son of the second marriage of his father Thomas Trevor, 1st Baron Trevor to Anne Bernard, née Weldon.
He studied at The Queen's College, Oxford, graduated in 1725 and then became a fellow of All Souls College, Oxford. In 1729 he was appointed as a clerk in the Secretary of State's office. In 1734 he went to the United Provinces as secretary to the embassy under Horatio Walpole. He succeeded as head of the embassy in 1739, initially as Envoy-Extraordinary, and from 1741 as Minister-Plenipotentiary. During this time he maintained a regular correspondence with Horace Walpole.
In 1750 he was appointed a Commissioner of the Revenue in Ireland. He took the additional surname of Hampden in 1754, on succeeding to the estates of his relative John Hampden. Twelve years after he had succeeded his brother as Baron Trevor, he was created, on 14 June 1776, Viscount Hampden, of Great and Little Hampden in the County of Buckingham.
From 1759 to 1765 he was joint Postmaster General. He wrote some Latin poems which were published at Parma in 1792 as Poemata Hampdeniana.
He first had an unacknowledged Fleet Marriage and had two sons, one of whom, the Rev. Dr John Trevor, (1740-1796) was appointed Rector of Goathurst in 1771, but who later moved to the Continent and eventually became Minister of the Protestant chapel at Ostend, where he died in 1796. He had five daughters by his first wife, one of whom was the seafarer Frances Barkley.
Trevor married secondly, on 6 Feb. 1743, at The Hague, Constantia, daughter of Peter Anthony de Huybert, lord of Van Kruyningen, by whom he left four children—Constantia, Thomas, second viscount Hampden, John Hampden-Trevor, third viscount Hampden [q. v.], and Anne. [1]
His second son, John Hampden-Trevor, 3rd Viscount Hampden (1749–1824), died only three weeks after he had succeeded his elder brother Thomas Hampden-Trevor, 2nd Viscount Hampden, when the titles became extinct.