Academia
- Jackson Armstrong (c. 1996) – University of Cambridge graduate and historian
- Arthur, James Greig (1962) – World's leading mathematician in representation theory and creator of the General Trace Formula
- Bethune, Charles James Stewart (1856) – Headmaster of Trinity College School and co-founder Entomological Society of Canada
- Biggar, James H. ρ (1926) – Founder of Visites Interprovinviales, later the Society for Educational Visits and Exchanges in Canada
- Clarkson, Stephen FRSC ρ (1954) – Foreign policy and Canadian history expert and Governor General's Award winner
- Crooks, Adam – First Chancellor of the University of Toronto and Attorney General of Canada
- Cooper, John Julius, 2nd Viscount Norwich CVO (1942) – British historian, travel writer, and television personality
- Crean, John Gale (1932) – Founding President of the Ontario Science Centre and the first Canadian director of International Chamber of Commerce
- Cruikshank, Ernest Alexander (1872) – Notable Canadian historian and founder of the Ontario Historical Society
- Denison, George Taylor III FRSC (1856) – Founder of Canada First and the Canadian National Association
- Eayrs, James (1938) – World renowned political scientist and Governor General's Award winner
- Eksteins, Modris ρ (1961) – Renowned historian of Germany
- Endicott, Timothy (1979) – First Dean of Law, University of Oxford
- Ewart, John S. QC – Prominent lawyer, Canadian historian, and advocate of Canadian independence
- Fleming, James Henry (1892) – Top Canadian ornithologist
- Grant, George P. OC FRSC (1936) – Philosopher and author
- Grier, Terry (c. 1954) – President of Ryerson University and New Democratic Party member of parliament
- Hayhurst, Jim (1959) – Chairman of Outward Bound, member of the Canadian Mount Everest expedition, and co-founder of Trails Youth Initiatives
- Hayhurst, Jim Jr. (1987) – Member of the Canadian Mount Everest expedition
- Ignatieff, Nicholas – Warden of Hart House, at the University of Toronto
- Keefer, Thomas (1838) – Noted aquatics civil engineer, president of the American Society of Civil Engineers, and founder of the Canadian Society for Civil Engineering
- Kilbourn, William CM FRSC (c. 1946) – University of Oxford and Harvard University graduate, author, historian, and executive of the Canada Council and Canadian commission for UNESCO
- Kilbourn, William Morley (1944) – Toronto historian and first president of Word on the Street
- Loudin, James FRSC (1858) – First physics professor at the University of Toronto and president of the Royal Society of Canada
- MacInnis, Dr. Joseph CM (1956) – Explorer, leader of the dive to film the RMS Titanic in IMAX, and the first person to dive under the North Pole
- Macklem, Michael CM – Founder of Oberon Press
- McNaught, Kenneth OC (c. 1936) – Historian and author
- Parmenter, Ross (1929) – Music editor at the New York Times and expert on indigenous Mexican culture
- Ryerson, Stanley Brehaut (c. 1929) – Historian and communist activist
- Singer, Peter (1978) – Director of Joint Centre for Bioethics at the University of Toronto and programme director at the Canadian Program on Genomics
- Stupart, Sir Robert Fredrick (1872) – Pioneer of public weather forecasts and director of the National Meteorological Society
- Tyrell, Joseph FRSC (1878) – Discoverer of dinosaur bones in Alberta and in whose honour the Royal Tyrrell Museum of Palaeontology is named
- Wright, Sir Charles Seymour (1904) – Team physicist on Robert Scott's Antarctic expedition and developer of the "trench wireless" during World War I
Read more about this topic: List Of Upper Canada College Alumni