By-elections to the 30th Canadian Parliament were held to fill vacancies in the House of Commons of Canada between the 1974 federal election and the 1979 federal election. The Liberal Party of Canada led a majority government for the entirety of the 30th Canadian Parliament, though their number did decrease from by-elections.

27 seats became vacant during the life of the Parliament. 25 of these vacancies were filled through by-elections, and 2 seats remained vacant when the 1979 federal election was called.

• List of federal by-elections in Canada

• Parliament of Canada–Elected in By-Elections Archived 2012-11-19 at the Wayback Machine