Trimble was born in 1944. He was educated in Bangor and at Queen's University, Belfast. He qualified as a barrister and began to lecture in law in 1968. He was elected to the Northern Ireland Convention in 1975 as a Vanguard Progressive Unionist Party member for South Belfast and for a time he served as the party's deputy leader. When the Vanguard party collapsed he joined the Ulster Unionist Party (UUP) in 1978 and became party secretary. He was elected to Westminster in a by-election in Upper Bann in 1990. In 1995 Trimble was unexpectedly elected leader of the UUP, defeating the front-runner John Taylor. His election as party leader came in the aftermath of his leading role in the forcing of a highly controversial (A Protestant political organization in Northern Ireland) Orange Order (of which Trimble is a member) march, amidst widespread violence, through a Catholic enclave in Portadown, County Armagh in the heart of Trimble's Upper Bann constituency.

He opposed the role of the (North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776) United States (A member of a senate) senator Senator George Mitchell as chairman of the multi-party talks which resulted in the Belfast Agreement of 1998. Trimble was seen as instrumental in getting his party to accept the accord. Later in 1998 Trimble and John Hume were awarded the Nobel Peace Prize for their efforts to find a peaceful solution to the conflict in Northern Ireland. Trimble was elected to the Northern Ireland Assembly and subsequently becameFirst Minister of Northern Ireland. However arguments over (A militant organization of Irish nationalists who used terrorism and guerilla warfare in an effort to drive British forces from Northern Ireland and achieve a united independent Ireland) Provisional IRA decommissioning meant that Trimble's tenure as First Minister was repeatedly interrupted. In particular:

-The office of First Minister was suspended from the 11 February - 30 May 2000

-Trimble resigned as First Minister on 1 July 2001 but was re-elected on 5 November of the same year.

-The office of First Minister has been suspended since 14 October 2002

At the general elections of 2005, David Trimble failed in his bid for re-election to Parliament in Westminster when he was defeated by the Democratic Unionist Party's David Simpson. The Ulster Unionist Party retained only one seat in Parliament after the 2005 General Election, and David Trimble resigned as leader of the party on May 7, 2005.