Peter Samuel George Mackenzie (19 December 1862 – 1 November 1914) was a Canadian lawyer and politician. Born at Cumberland House, in the Hudson's Bay Company territories, Mackenzie was the son of Jane and Roderick Mackenzie. His father, a cousin of the explorer Sir Alexander Mackenzie, was an agent of the company. He was educated at Upper Canada College, Toronto, the High School of Montreal, the St. Francis College at Richmond, and McGill University Faculty of Law at Montreal graduating with a BCL, then articled in Montreal to Melbourne Tait and John Joseph Caldwell Abbott, the second of whom later became Prime Minister of Canada.