Born in Swanmore, Hampshire, England, at age six he and his family moved to Canada, settling on a farm in Egypt, Ontario, near the shores of Lake Simcoe. While the family had been comfortable in England, the farm in Georgina Township of York County was not a success and Leacock's family was quite poor. His father Peter suffered from alcoholism, becoming a violent alcoholic.
Leacock, always of obvious intelligence, was sent to the elite private school of Upper Canada College in Toronto, where he was top of the class and so popular he was chosen as head boy. His father left the house in 1887 and never returned. The same year, seventeen year-old Leacock started at University College at the University of Toronto, where he was admitted to the Zeta Psi fraternity, but found he could not resume the following year due to financial difficulties.
He left university to earn money as a schoolteacher - a job he disliked immensely - at Strathroy, Uxbridge and finally in Toronto. As a teacher at Upper Canada College, his alma mater, he was able to simultaneously attend classes at the University of Toronto and, in 1891, earn his degree through part-time studies. It was during this period that his first writing was published in The Varsity, a campus newspaper.
Disillusioned with teaching, in 1899 he began graduate studies at the University of Chicago where he received a doctorate in political science and political economy. He moved from Chicago, Illinois to Montreal, Quebec where he became a lecturer and long-time acting head of the political economy department at McGill University.
He was closely associated with Sir Arthur Currie, former commander of the Canadian Corps in the Great War and principal of McGill from 1919 until his death in 1933. In fact, Currie had been a student observing Leacock's practice teaching in Strathroy in 1888. In 1936, Leacock was forcibly retired by the McGill Board of Governors -- an unlikely prospect had Currie lived.
Leacock was both a social conservative and a partisan Conservative. He opposed women's rights and disliked non-Anglo-Saxon immigration. He was, however, a supporter of social welfare legislation. He was a champion of the British Empire, and went on lecture tours to further the cause.
Although he was considered as a federal candidate for his party, it declined to invite the author, lecturer and maverick to stand for election. Nevertheless, he would stump for local candidates at his summer home.
Early in his career Leacock turned to fiction, humour, and short reports to supplement (and ultimately exceed) his regular income. His stories, first published in magazines in Canada and the United States and later in novel form became extremely popular around the world. It was said in 1911 that more people had heard of Stephen Leacock than had heard of Canada.
During the summer months, he lived at Old Brewery Bay in Orillia, across Lake Simcoe from where he was raised and also bordering Lake Couchiching. The cottage is now a museum and National Historic Site, and he also let a small farm. Gossip provided by the local barber, Jefferson Short, provided Leacock with the material which would become Sunshine Sketches of a Little Town (1912), set in the thinly-disguised Mariposa.
Although he wrote learned articles and books related to his field of study, his political theory is now all but forgotten. Leacock was awarded the Royal Society of Canada's Lorne Pierce Medal in 1937, nominally for his academic work.
Leacock was predeceased by his wife and survived by his son Stephen Jr. In accordance with his wishes, after his death due to throat cancer, he was cremated and buried at Sibbald Point in Georgina Township near his boyhood home and across Lake Simcoe from his adult summer home.
Shortly after his death, Barbara Nimmo, his niece, literary executor and benefactor, published two major posthumous works: Last Leaves (1945) and The Boy I Left Behind Me (1946). His physical legacy was less treasured, and his abandoned summer cottage became derelict. It was rescued from oblivion when it was declared a National Historic Site in 1958 and ever since has operated as a museum called the Stephen Leacock Memorial Home.
In 1947, the Stephen Leacock Award was created to recognize the best in Canadian literary humour. In the 1960s, McGill University named an arts building and a library room after its well-known professor. In 1969, the centennial of his birth, Canada Post issued a six cent stamp with his image on it. The following year, the Stephen Leacock Centennial Committee had a plaque erected at his English birthplace and a mountain in the Yukon was named after him.
A public high school in Scarborough, Ontario, Stephen Leacock Collegiate, is named after the author. It is joined to John Buchan Middle School.
A theatre in Keswick, Ontario is also named after him.
A main building of offices and lecture halls at McGill University is also named after him.