Thomas Douglas, 5th Earl of Selkirk FRS FRSE was a Scottish peer. He was noteworthy as a Scottish philanthropist who sponsored immigrant settlements in Canada at the Red River Colony.

The Red River Colony, also known as Assiniboia, was a colonization project set up in 1811 by Thomas Douglas, 5th Earl of Selkirk, on 300,000 square kilometres (120,000 sq mi) of land in British North America. This land was granted to Douglas by the Hudson's Bay Company in the Selkirk Concession. It included portions of Rupert's Land, or the watershed of Hudson Bay, bounded on the north by the line of 52° N latitude roughly from the Assiniboine River east to Lake Winnipegosis. It then formed a line of 52° 30′ N latitude from Lake Winnipegosis to Lake Winnipeg, and by the Winnipeg River, Lake of the Woods and Rainy River.