The 1918 United States Senate special election in Missouri took place on November 5, 1918 in Missouri. DemocratWilliam J. Stone was elected to the full term in 1914, but died on April 14, 1918. Xenophon P. Wilfley was appointed to the vacant seat on April 30, 1918. He lost the Democratic primary election to Joseph W. Folk, who was defeated by RepublicanSelden P. Spencer in the general election.