The 1920 United States Senate election in Missouri took place on November 2, 1920, in Missouri. The incumbent Republican Senator, Selden P. Spencer, was re-elected to a full term, having won a special election in 1918. He defeated Breckinridge Long of the Democratic Party. Spencer underperformed Republican presidential nominee Warren G. Harding, who won 54.6% of the vote in the concurrent presidential election.
The FarmerâÂÂWorker Party nominated carpenter W. J. Mallett.
The Socialist Labor Party nominated Andrew Trudell.