Unionism in Ireland is a political tradition that professes loyalty to the crown of the United Kingdom and to the union it represents with England, Scotland and Wales. The overwhelming sentiment of Ireland's Protestant minority, unionism mobilised in the decades following Catholic Emancipation in 1829 to oppose restoration of a separate Irish parliament. Since Partition in 1921, as Ulster unionism its goal has been to retain Northern Ireland as a devolved region within the United Kingdom and to resist the prospect of an all-Ireland republic. Within the framework of the 1998 Belfast Agreement, which concluded three decades of political violence, unionists have shared office with Irish nationalists in a reformed Northern Ireland Assembly. As of February 2024, they no longer do so as the larger faction: they serve in an executive with an Irish republican (Sinn Féin) First Minister.
Unionism became an overarching partisan affiliation in Ireland late in the nineteenth century. Typically Presbyterian agrarian-reform Liberals coalesced with traditionally Anglican, Orange Order allied, Conservatives against the Irish Home Rule Bills of 1886 and 1893. Joined by loyalist labour, on the eve of World War I this broad opposition to Irish self-government concentrated in Belfast and its hinterlands as Ulster unionism and prepared an armed resistance—the Ulster Volunteers.
