In 1946, her family moved to England when her father, a doctor in the navy, went there to study for a year. Margaret MacMillan would only return to England at age 15 when she was sent there to complete high school before returning to her family in Canada.
She received her B.A. from U of T before receiving her Ph.D. from Oxford University. From 1975 to 2002 she was a professor at Ryerson University in Toronto. She is the author of Women of the Raj, a selection of the "History Book Club." In addition to numerous articles and reviews on a variety of Canadian and world affairs, Ms. Macmillan has co-edited books dealing with Canada's international relations, including with NATO, and with Canadian-Australian relations.
Her most successful and celebrated work is Paris 1919: Six Months That Changed the World which won the Duff Cooper Prize for an outstanding literary work in the field of history, biography or politics; the Hessell-Tiltman Prize for History; the most prestigious Samuel Johnson Prize for the best work of non-fiction published in the United Kingdom; and the 2003 Governor General's Literary Award in Canada.
She teaches courses on the history of international relations, including a seminar on the history of the Cold War.