The 1940 United States Senate elections coincided with the election of Franklin D. Roosevelt to his third term as president. The 32 seats of Class 1 were contested in regular elections, and special elections were held to fill vacancies.

The Minnesota Farmer–Labor Party (FLP) was a left-wing American political party in Minnesota between 1918 and 1944. The FLP largely dominated Minnesota politics during the Great Depression. It was one of the most successful statewide third party movements in United States history and the longest-lasting affiliate of the national Farmer–Labor movement. At its height in the 1920s and 1930s, FLP members included three Minnesota governors, four United States senators, eight United States representatives and a majority in the Minnesota legislature.