The Ulster Protestant community emerged during the Plantation of Ulster. This was the colonisation of Ulster with loyal English-speaking Protestants from Great Britain under the reign of King James. Those involved in planning the plantation saw it as a means of controlling, anglicising, and "civilising" Ulster. The province was almost wholly Gaelic, Catholic and rural, and had been the region most resistant to English control. The plantation was also meant to sever Gaelic Ulster's links with the Gaelic Highlands of Scotland. Most of the land colonised was confiscated from the native Irish. Begun privately in 1606, the plantation became government-sponsored in 1609, with much land for settlement being allocated to the Livery Companies of the City of London. By 1622 there was a total settler population of about 19,000, and by the 1630s somewhere between 50,000 and as many as 80,000. Another influx of an estimated 20,000 Scottish Protestants, mainly to the coastal counties of Antrim, Down and Londonderry, was a result of the seven ill years of famines in Scotland in the 1690s. This migration decisively changed the population of Ulster, giving it a Protestant majority. While Presbyterians of Scottish descent and origin had already become the majority of Ulster Protestants by the 1660s, when Protestants still made up only a third of the population, they had become an absolute majority in the province by the 1720s. Divisions between Ulster's Protestants and Irish Catholics have played a major role in the history of Ulster from the 17th century to the present day. It has led to bouts of violence and political upheaval, notably in the Irish Confederate Wars, the Williamite War, the Armagh disturbances, the Irish revolutionary period, and the Troubles. There were also tensions between the two main groups of Ulster Protestants; Scottish Protestant migrants to Ulster were mostly Presbyterian and English Protestants mostly Anglican. The Penal Laws discriminated against both Catholics and Presbyterians, in an attempt to force them to accept the state religion, the Anglican Church of Ireland. Repression of Presbyterians by Anglicans intensified after the Glorious Revolution, especially after the Test Act of 1703, and was one reason for heavy onward emigration to North America by Ulster Presbyterians during the 18th century. Between 1717 and 1775, an estimated 200,000 migrated to what became the United States of America. Some Presbyterians also returned to Scotland during this period, where the Presbyterian Church of Scotland was the state religion. These Penal Laws are partly what led Ulster Presbyterians to become founders and members of the United Irishmen, a republican movement which launched the Irish Rebellion of 1798. Repression of Presbyterians largely ended after the rebellion, with the relaxation of the Penal Laws. The Kingdom of Ireland became part of the United Kingdom in 1801. As Belfast became industrialised in the 19th century, it attracted yet more Protestant immigrants from Scotland. After the partition of Ireland in 1920, the new government of Northern Ireland launched a campaign to entice Protestants from the Irish Free State to relocate to Northern Ireland, with inducements of state jobs and housing, and large numbers accepted.
The vast majority of Ulster Protestants live in Northern Ireland, which is part of the United Kingdom. Most tend to support the Union with Great Britain, and are referred to as unionists. Unionism is an ideology that has been divided by some into two camps; Ulster British, who are attached to the United Kingdom and identify primarily as British; and Ulster loyalists, whose politics are primarily ethnic, prioritising their Ulster Protestantism above their British identity. The Loyal Orders, which include the Orange Order, Royal Black Institution and Apprentice Boys of Derry, are exclusively Protestant fraternal organisations which originated in Ulster and still have most of their membership there. About 3% of Ulster Protestants live in the three counties of Ulster now in the Republic of Ireland, Cavan, Monaghan, and Donegal, where they make up around a fifth of the Republic's Protestant population. Unlike Protestants in the rest of the Republic, some retain a sense of Britishness, and a small number have difficulty identifying with the independent Irish state. Most Ulster Protestants speak Ulster English, and some on the north-east coast speak with the Ulster Scots dialects. A very small number have also learned the Irish language as a second language.