Gustave Lanctot OC, QC, FRSC, also spelled Gustave Lanctôt, (5 July 1883 – 2 February 1975) was a Canadian historian and archivist. Born in Saint-Constant, Quebec, he studied law at Université de Montréal and was called to the Quebec Bar in 1907. A Rhodes Scholar, he studied political science and history from 1909 to 1911 while at Oxford University. He was also a member of the Oxford Canadians ice hockey team. In 1912, he joined the National Archives of Canada. During World War I, he served in the Canadian Expeditionary Force.