William Mactavish was a Scottish Hudson's Bay Company clerk, accountant, and chief trader. Mainly known for his dual-position as Governor of Assiniboia, and Governor of Rupert's Land, he played a major role in the development of Western Canada. Mactavish is frequently criticized for his role in the Red River Rebellion.

The Red River Rebellion, also known as the Red River Resistance, Red River uprising, or First Riel Rebellion, was the sequence of events that led up to the 1869 establishment of a provisional government by Métis leader Louis Riel and his followers at the Red River Colony, in the early stages of establishing today's Canadian province of Manitoba. It had earlier been a territory called Rupert's Land and been under control of the Hudson's Bay Company before it was sold.