TREVOR, SIR JOHN (1626–1672), English politician, was a son of Sir John Trevor (d. 1673) of Trevelyn, Denbighshire. His father was a member of parliament under James I. and Charles I., and sat also in the parliaments of Oliver and of Richard Cromwell, and was a member of the council of state during the Commonwealth. One of his uncles was Sir Sackvill Trevor (d. c. 1640), a naval officer, who was knighted in 1604; and another was Sir Thomas Trevor (1586–1656), the judge who decided in favour of the Crown in the famous case about the legality of ship-money, and was afterwards impeached and fined. Sir John Trevor was returned to parliament in 1646 as member for Flintshire. After filling several public positions under the Commonwealth and Protectorate he was a member of the council of state appointed in February 1660 and under Charles II. he rose to a high position. Having purchased the office of secretary of state he was knighted and entered upon its duties towards the end of 1668, just after he had helped to arrange an important treaty between England and France. He married Ruth, daughter of the great John Hampden, and died on the 28th of May 1672.
His second son, Thomas, Baron Trevor (1658–1730), was knighted in 1692 as solicitor-general and in 1695 became attorney-general. In 1701 he was appointed chief justice of the common pleas, and in 1712 he was created a peer as Baron Trevor of Bromham. On the accession of George I. in 1714 he was deprived of the justiceship, but from 1726 to 1730 he was lord privy seal. Three of his sons succeeded in turn to his barony, and a fourth son, Richard Trevor (1707–1771), was bishop of St Davids from 1744 to 1752, and then bishop of Durham. Robert, 4th Baron Trevor and 1st Viscount Hampden (1706–1783), represented his country at the Hague from 1739 to 1746, during which time he maintained a regular correspondence with Horace Walpole. He took the additional name of Hampden in 1754, on succeeding to the estates of that family, and in 1776, twelve years after he had become Baron Trevor, he was created Viscount Hampden. From 1759 to 1765 he was joint postmaster-general. He wrote some Latin poems which were published at Parma in 1792 as Poemata Hampdeniana. His second son, John Hampden-Trevor (1749–1824), British minister at Munich from 1780 to 1783 and at Turin from 1783 to 1798, died only three weeks after he had succeeded his brother Thomas as 3rd Viscount Hampden, the titles becoming extinct.
Another member of this family was Sir John Trevor (1637–1717), Speaker of the House of Commons (1685). A partisan of James II., he was deprived of his office on the accession of William III., but in 1690 he was again a member of parliament, becoming Speaker for the second time in 1690 and master of the rolls in 1693. In 1695 he was found guilty of accepting a bribe and was expelled from the House of Commons, but he retained his judicial position until his death on the 20th of May 1717. Through his daughter Anne Sir John was the ancestor of the Hills, marquesses of Downshire, and of the family of Hill-Trevor, Viscounts Dungannon from 1766 to 1862.