Ulster_Unionist_Party The Ulster Unionist Party (UUP, sometimes referred to as the Official Unionist Party or OUP or, in a historic sense, simply the Unionist Party) is the more moderate of the two main unionist political parties in Northern Ireland. Prior to the split in Unionism in the late 1960s, when the former Protestant Unionist Party began to attract more hard line support away from the UUP, it governed Northern Ireland between 1921 and 1972 as the sole Unionist party.