The DUP was founded in 1971 by the Reverend Ian Paisley and William Boal, an MP who defected from the Official Unionists in protest at the reform policies of the then prime minister of Northern Ireland, Terence O'Neill.
The DUP led successful opposition to the power-sharing executive in 1974 and has set itself against any measure that it perceives as threatening the union with Britain, including the Good Friday Agreement.
It is the most hardline - politically and religiously - of the unionist parties, and the largest Northern Ireland party in terms of representation at Westminster, having overtaken the Ulster Unionists as the main unionist party in 2005.
In a surprise move, Reverend Paisley met Republic of Ireland taoiseach Bertie Ahern in 2004.
But the DUP remains implacably opposed to sharing power with Sinn Fein until the republican party has 'fulfilled its obligations' with respect to ensuring the IRA never returns to violent conflict