The 21st Legislative Assembly of Quebec was the provincial legislature in Quebec, Canada that existed from October 25, 1939, to August 8, 1944. The Quebec Liberal Party led by Adélard Godbout was the governing party. It was the last term for the Liberals in power until 1960. The Union Nationale were in power for the following four terms.

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• After the 1939 elections

This was the list of members of the Legislative Assembly of Quebec that were elected in the 1939 election:

Other MLAs were elected in by-elections during this term

• Joseph-Tancrède Labbé, Union Nationale, Mégantic, November 19, 1940
• Damase Perrier, Quebec Liberal Party, Terrebonne, November 19, 1940
• Dennis James O'Connor, Quebec Liberal Party, Huntingdon, October 6, 1941
• Jean-Paul Beaulieu, Union Nationale, Saint-Jean-Napierville, October 6, 1941
• Thomas Guérin, Quebec Liberal Party, Montréal-Sainte-Anne, March 23, 1942
• Claude Jodoin, Quebec Liberal Party, Montréal-Saint-Jacques, March 23, 1942
• Joseph-Willie Robidoux, Quebec Liberal Party, Richelieu-Verchères, March 23, 1942
• George Carlyle Marler, Quebec Liberal Party, Westmount-Saint-Georges, March 23, 1942

• Prime Minister and Executive Council President: Adélard Godbout
• Agriculture: Adélard Godbout
• Colonization: Adélard Godbout (1939-1942), Cléophas Bastien (1942-1944)
• Labour: Edgar Rochette
• Public Works: Télesphore-Damien Bouchard (1939-1942), Georges-Étienne Dansereau (1942-1944)
• Health: Henri Groulx (1939-1941)
• Social Welfare: Henri Groulx (1940-1941)
  • Health and Social Welfare:Henri Groulx (1941-1944)
• Lands, Forests, Hunting and Fishing: Pierre-Émile Côté (1939-1941)
  • Lands and Forests: Pierre-Émile Côté (1941-1942), Wilfrid Hamel (1942-1944)
  • Hunting and Fishing: Pierre-Émile Côté (1941-1942), Valmore Bienvenue (1942-1944)
• Mines and Fisheries: Edgar Rochette (1939-1941)
  • Mines and coastal fisheries: Edgar Rochette (1941-1942)
    • Mines: Edgar Rochette (1942-1944)
• Roads: Télesphore-Damien Bouchard (1939-1944), Georges-Étienne Dansereau (1944)
• Municipal Affairs, Industry and Commerce: Oscar Drouin (1939-1944), Henri-René Renault (1944)
• Attorney General: Wilfrid Girouard (1939-1942), Léon Casgrain (1942-1944)
• Provincial Secretary: Henri Groulx (1939-1940), Hector Perrier (1940-1944)
• Treasurer: James Arthur Matthewson
• Members without portfolios: Frank Lawrence Connors, Georges-Étienne Dansereau (1939-1942), Léon Casgrain (1939-1942), Louis-Joseph Thisdel, Cléophas Bastien (1939-1942), Wilfrid Hamel (1939-1942), Francois-Philippe Brais (1940-1944), Perrault Casgrain (1942-1944), Henri-René Renault (1942-1944), Joseph-Achille Francoeur (1944), Maurice Gingues (1944)

The electoral map was reformed in 1944 which was used in the upcoming election later that year. Some of the changes included de-mergers of ridings that were created in the previous reform in 1939.

• Abitibi was split into two ned ridings: Abitibi-Ouest and Abitibi-Est.
• Rouyn-Noranda was formed from parts of Témiscamingue.
• The riding of Napierville-Laprairie was recreated after Châteauguay and Laprairie were de-merged as well as Saint-Jean and Napierville which formed Saint-Jean-Napierville in 1939. Châteauguay and Saint-Jean were reformed as individual ridings.
• Richelieu and Verchères, which formed Richelieu-Verchères returned as individual ridings.
• Kamouraska and Rivière-du-Loup which formed Kamouraska-Rivière-du-Loup returned as individual ridings.

• List of Historical Cabinet Ministers