The Plantation of Ulster was the organised colonisation (plantation) of Ulster – a province of Ireland – by people from Great Britain during the reign of King James VI and I. Most of the settlers came from southern Scotland and northern England; their culture differed from that of the native Irish. Small privately funded plantations by wealthy landowners began in 1606, while the official plantation began in 1609. Most of the land had been confiscated from the native Gaelic chiefs, several of whom had fled Ireland for mainland Europe in 1607 following the Nine Years' War against English rule. The official plantation comprised an estimated half a million acres (2,000 km2) of arable land in counties Armagh, Cavan, Fermanagh, Tyrone, Donegal, and Londonderry. Land in counties Antrim, Down, and Monaghan was privately colonised with the king's support.

James VI and I was King of Scotland as James VI from 24 July 1567 and King of England and Ireland as James I from the union of the Scottish and English crowns on 24 March 1603 until his death in 1625. Although he long tried to get both countries to adopt a closer political union, the kingdoms of Scotland and England remained sovereign states, with their own parliaments, judiciaries, and laws, ruled by James in personal union. He was the longest-reigning monarch of the Kingdom of Scotland.