The Loyal Orange Institution, commonly known as the Orange Order, is an international Protestant fraternal order based in Northern Ireland and primarily associated with Ulster Protestants, it also has lodges in England, Scotland and the Republic of Ireland, as well as in parts of the Commonwealth of Nations and the United States. The Orange Order was founded by Ulster Protestants in County Armagh in 1795, during a period of Protestant–Catholic sectarian conflict, as a fraternity sworn to maintain the Protestant Ascendancy in Ireland. It is headed by the Grand Orange Lodge of Ireland, established in 1798. Its name is a tribute to the Dutch-born Protestant king William of Orange, who defeated Catholic king James II in the Williamite–Jacobite War (1688–1691). The order is best known for its yearly marches, the biggest of which are held on or around 12 July (The Twelfth), a public holiday in Northern Ireland.

The Orange Order is a conservative, British unionist and Ulster loyalist organisation. Thus it has traditionally opposed Irish nationalism/republicanism and campaigned against Scottish independence. The Order sees itself as defending Protestant civil and religious liberties, whilst critics accuse it of being sectarian, triumphalist and supremacist. It does not accept non-Protestants as members unless they convert and adhere to the principles of Orangeism, nor does it accept Protestants married to Catholics. Orange marches through Catholic neighbourhoods are controversial and have often led to violence, such as the Drumcree conflict.