Iron County is a county located in the Lead Belt region in the U.S. state of Missouri. As of the 2020 census, the population was 9,537. The largest city and county seat is Ironton. Iron County was officially organized on February 17, 1857, and was named after the abundance of iron ore found within its borders.

The 2018 United States Senate election in Missouri took place on November 6, 2018, to elect a member of the United States Senate to represent the State of Missouri, concurrently with other elections to the United States Senate, elections to the United States House of Representatives, and various state and local elections, including Missouri's quadrennial State Auditor election.