By-elections to the 40th Canadian Parliament were held to fill vacancies in the House of Commons of Canada between the 2008 federal election and the 2011 federal election. The Conservative Party of Canada led a minority government for the entirety of the 40th Canadian Parliament, with little change from by-elections.
Ten seats became vacant during the life of the Parliament. Seven of these vacancies were filled through by-elections, and three seats remained vacant when the 2011 federal election was called.