William David Trimble, Baron Trimble, (15 October 1944 – 25 July 2022) was a British politician who was the first First Minister of Northern Ireland from 1998 to 2002, and leader of the Ulster Unionist Party (UUP) from 1995 to 2005. He was also Member of Parliament (MP) for Upper Bann from 1990 to 2005 and Member of the Legislative Assembly (MLA) for Upper Bann from 1998 to 2007.

Trimble began his career teaching law at The Queen's University of Belfast in the 1970s, during which time he began to get involved with the paramilitary-linked Vanguard Progressive Unionist Party (VPUP). He was elected to the Northern Ireland Constitutional Convention in 1975, and joined the UUP in 1978 after the VPUP disbanded. Remaining at Queen's University, he continued his academic career until being elected as the MP for Upper Bann in 1990. In 1995 he was unexpectedly elected as the leader of the UUP. He was instrumental in the negotiations that led to the Good Friday Agreement in 1998, and (along with John Hume) won the Nobel Peace Prize that year for his efforts. He was later elected to become the first First Minister of Northern Ireland, although his tenure was turbulent and frequently interrupted by disagreements over the timetable for Provisional Irish Republican Army decommissioning.

Trimble resigned the leadership of the UUP soon after being defeated at the 2005 general election. In June 2006, he accepted a life peerage in the House of Lords, taking the title of Baron Trimble, of Lisnagarvey in the County of Antrim. He did not stand again for the Assembly, which finally reconvened in 2007, instead leaving the UUP to join the Conservative Party.