The 2005 Ulster Unionist Party leadership election began on 7 May 2005 when David Trimble resigned as leader of the Ulster Unionist Party following his party's poor performance in the 2005 general election when it lost all but one of its seats, including Trimble's own. Following his resignation, the UUP's executive committee charged Sir Reg Empey, Lady Hermon and Lord Rogan with the interim leadership of the Party.

The Ulster Unionist Party (UUP) is a unionist political party in Northern Ireland. The party was founded as the Ulster Unionist Council in 1905, emerging from the Irish Unionist Alliance in Ulster. Under Edward Carson, it led unionist opposition to the Irish Home Rule movement. Following the partition of Ireland, it was the governing party of Northern Ireland between 1921 and 1972. It was supported by most unionist voters throughout the conflict known as the Troubles, during which time it was often referred to as the Official Unionist Party (OUP).