Jack Granatstein was born in Toronto in 1939. He attended Toronto public schools, Le Collège Militaire Royal de St-Jean (Grad. Dipl., 1959), the Royal Military College, Kingston (B.A., 1961), the University of Toronto (M.A., 1962), and Duke University (PhD., 1966). He served in the Canadian Army (1956–1966), then joined the History Department at York University, Toronto (1966–1995) where, after taking early retirement in 1995, he is Distinguished Research Professor of History Emeritus.
In 1995, Jack Granatstein served as one of three commissioners on the Special Commission on the Restructuring of the Canadian Forces Reserves, and in 1997, he advised the Minister of National Defence on the future of the Canadian Forces. He served as the Director and CEO of the Canadian War Museum (1998–2001). He is also co-chair of the Council for Canadian Security in the 21st Century.
Granatstein has held the Canada Council's Killam senior fellowship twice, was editor of the Canadian Historical Review (1981–1984), and is a Fellow of the Royal Society of Canada. The Royal Society awarded him the J.B. Tyrell Historical Gold Medal (1992) “for outstanding work in the history of Canada,” and his book The Generals (1993) won the J.W. Dafoe Prize and the UBC Medal for Canadian Biography. Memorial University of Newfoundland gave him an honorary Doctor of Letters (1993) and the University of Calgary an honorary Doctor of Laws (1994). He is a member of the Royal Military College of Canada Board of Governors. The Conference of Defence Associations Institute named him winner of The Vimy Award "for achievement and effort in the field of Canadian defence and security" in 1996. He is an Officer of the Order of Canada (1997).
His areas of research include 20th Century Canadian national history — foreign and defence policy, Canadian-American relations, the military, the public service, and politics. He comments regularly on historical questions and public affairs in the press and on radio and television; and he speaks regularly here and abroad. In 1995 the Minister of National Defence named him to the Special Commission on the Restructuring of the Canadian Forces Reserves (chaired by the Rt. Hon. Brian Dickson, former Chief Justice of Canada).
His many scholarly and popular books include most recently:
- Who Killed Canadian History? (1998, 1999)
- Trudeau's Shadow: The Life and Legacy of Pierre Elliott Trudeau
- Prime Ministers: Rating the Prime Ministers (1999, 2000)
- Our Century (2000)
- Who Killed the Canadian Military? (2002)
- First Drafts: Eye Witness Accounts in Canadian History (2003) and
- Battle Lines: Eyewitness Accounts from Canada's Military Past (2004).