# By-elections to the 30th Canadian Parliament

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.
| By-election | Date | Incumbent | Party | Winner | Party | Cause | Retained |
| Burnaby—Richmond—Delta | October 16, 1978 | John Reynolds | Progressive Conservative | Tom Siddon | Progressive Conservative | Resignation | Yes |
| St. Boniface | October 16, 1978 | Joseph-Philippe Guay | Liberal | Jack Hare | Progressive Conservative | Resignation | No |
| Fundy—Royal | October 16, 1978 | Gordon Fairweather | Progressive Conservative | Robert Corbett | Progressive Conservative | Resignation | Yes |
| Humber—St. George's—St. Barbe | October 16, 1978 | Jack Marshall | Progressive Conservative | Fonse Faour | New Democratic | Resignation | No |
| Halifax—East Hants | October 16, 1978 | Bob McCleave | Progressive Conservative | Howard Edward Crosby | Progressive Conservative | Resignation | Yes |
| Broadview | October 16, 1978 | John Gilbert | New Democratic | Bob Rae | New Democratic | Resignation | Yes |
| Eglinton | October 16, 1978 | Mitchell Sharp | Liberal | Rob Parker | Progressive Conservative | Resignation | No |
| Hamilton—Wentworth | October 16, 1978 | Sean O'Sullivan | Progressive Conservative | Geoff Scott | Progressive Conservative | Resignation | Yes |
| Ottawa Centre | October 16, 1978 | Hugh Poulin | Liberal | Robert de Cotret | Progressive Conservative | Resignation | No |
| Parkdale | October 16, 1978 | Stan Haidasz | Liberal | Yuri Shymko | Progressive Conservative | Resignation | No |
| Rosedale | October 16, 1978 | Donald S. Macdonald | Liberal | David Crombie | Progressive Conservative | Resignation | No |
| York—Scarborough | October 16, 1978 | Robert Stanbury | Liberal | W. Paul McCrossan | Progressive Conservative | Resignation | No |
| Lotbinière | October 16, 1978 | André Fortin | Social Credit | Richard Janelle | Social Credit | Death | Yes |
| Saint-Hyacinthe | October 16, 1978 | Claude Wagner | Progressive Conservative | Marcel Ostiguy | Liberal | Resignation | No |
| Westmount | October 16, 1978 | Bud Drury | Liberal | Don Johnston | Liberal | Resignation | Yes |
| Malpeque | May 24, 1977 | J. Angus MacLean | Progressive Conservative | Donald Wood | Liberal | Resignation | No |
| Langelier | May 24, 1977 | Jean Marchand | Liberal | Gilles Lamontagne | Liberal | Resignation | Yes |
| Louis-Hébert | May 24, 1977 | Albanie Morin | Liberal | Dennis Dawson | Liberal | Death | Yes |
| Témiscamingue | May 24, 1977 | Réal Caouette | Social Credit | Gilles Caouette | Social Credit | Death | Yes |
| Terrebonne | May 24, 1977 | Joseph-Roland Comtois | Liberal | Joseph-Roland Comtois | Liberal | Resignation | Yes |
| Verdun | May 24, 1977 | Bryce Mackasey | Liberal | Raymond Savard | Liberal | Resignation | Yes |
| St. John's West | October 18, 1976 | Walter Carter | Progressive Conservative | John C. Crosbie | Progressive Conservative | Resignation | Yes |
| Ottawa—Carleton | October 18, 1976 | John Turner | Liberal | Jean Pigott | Progressive Conservative | Resignation | No |
| Restigouche | October 14, 1975 | Jean-Eudes Dubé | Liberal | Maurice Harquail | Liberal | Resignation | Yes |
| Hochelaga | October 14, 1975 | Gérard Pelletier | Liberal | Jacques Lavoie | Progressive Conservative | Resignation | No |