William Aberhart was born on a farm near Kippen, Ontario. He attended a local public school and several colleges, receiving teacher's training. Some time later, in 1911, he earned a Bachelor of Arts degree from Queen's University in Kingston, Ontario.
Aberhart taught public school in several areas in Southern Ontario, including Wingham and Brantford, and was appointed Principal of Brantford Central Public School in 1905. During his time in Brantford, he volunteered much time to his devout Baptist faith, preaching at local churches and holding regular Bible studies.
In 1902, Aberhart married Jessie Flatt, with whom he had two daughters, Ola Janet and Khona Louise.
In 1918, Aberhart began a Bible study group in Calgary, Alberta which grew steadily year-by-year; by 1923, the Palace Theatre had to be rented to accomodate those interested in Aberhart's message. In 1927, Aberhart was appointed Dean of the newly-founded Calgary Prophetic Bible Institute. The institute's building served as a centre of worship, radio broadcast, and biblical studies. Aberhart's Sunday broadcasts proved as popular as his Bible studies as they drew regular listeners across the Canadian mid-west, and some listeners in the northern United States.
Aberhart became interested in politics during the Great Depression, a time which was especially harsh on Albertan farmers. Particularly, he was drawn the "social credit" theories of Major C. H. Douglas, a Scottish engineer. From 1932 to 1935, Aberhart lobbied for the United Farmers of Canada to adopt these theories, whereby the difference in production cost and individuals' purchasing power would be supplemented through government grants. When these efforts failed, Aberhart helped found Alberta's Social Credit Party, which won the 1935 provincial election by a landslide and remained in power in the province until 1968. Aberhart served as Premier of Alberta, Minister of Education and, starting in 1937, Attorney General during his tenure with the party.
Aberhart died unexpected on May 23, 1943 during a visit to Vancouver, British Columbia. He was succeeded by Ernest Manning as the Premier of Alberta.
The Aberhart Centre, a long-term medical care centre in Edmonton, Alberta, is named in his honour, as is a high school in Calgary.