List of Ontario by-elections

The list of Ontario by-elections includes every by-election held in the Canadian province of Ontario. By-elections occur whenever there is a vacancy in the Legislative Assembly, although an imminent general election may allow the vacancy to remain until the dissolution of parliament.

Causes

A by-election occurs whenever there is a vacancy in the Ontario legislature. Vacancies can occur for the following reasons:

Death of a member.
Resignation of a member.
Voided results
Expulsion from the legislature.
Ineligibility to sit.

When there is a vacancy, a by-election must be called within six months. Under amendments to the Election Act approved in 2016, a by-election is no longer required when a vacancy occurs in the 12 months leading up to a fixed general election date.

Ministerial by-elections

The list includes ministerial by-elections which occurred due to the requirement that incumbent members recontest their seats upon being appointed to Cabinet. These by-elections were almost always uncontested. This requirement was amended in 1926 to exempt ministers appointed within three months after a general election. In 1941 it was abolished
completely.

40th Legislative Assembly of Ontario 2011–2014

36th Legislative Assembly of Ontario 1995–1999

32nd Legislative Assembly of Ontario 1981–1985

30th Legislative Assembly of Ontario 1975–1977

''no by-elections''

26th Legislative Assembly of Ontario 1959–1963

25th Legislative Assembly of Ontario 1955–1959

† Won by acclamation

21st Legislative Assembly of Ontario 1943–1945

20th Legislative Assembly of Ontario 1937–1943

† Won by acclamation
*Though nominally an "Independent-Liberal", MacBride was a supporter of the Liberal government and was a cabinet minister at the time of his death