The 1940 Australian federal election was held in Australia on 21 September 1940. All 74 seats in the House of Representatives and 19 of the 36 seats in the Senate were up for election. The incumbent Coalition, consisting of the United Australia Party led by Prime Minister Robert Menzies and the Country Party led by Archie Cameron, defeated the opposition Labor Party under John Curtin despite losing the overall popular vote.

Lang Labor was a faction of the Australian Labor Party (ALP) consisting of the supporters of Jack Lang, who served two terms as Premier of New South Wales and was the party's state leader from 1923 to 1939. It controlled the New South Wales branch of the ALP throughout most of the 1920s and 1930s. The faction broke away to form separate parliamentary parties on several occasions and stood competing candidates against the ALP in state and federal elections.