Lafayette County is a county in the western portion of Missouri, part of the Kansas City metropolitan area. As of the 2020 census, the population was 32,984. Its county seat is Lexington. The county was organized November 16, 1820, from Cooper County and originally named Lillard County for James Lillard of Tennessee, who served in the first state constitutional convention and first state legislature. It was renamed Lafayette County on February 16, 1825, in honor of Revolutionary War hero the Marquis de La Fayette, who was then visiting the United States.

Lexington is a city in, and the county seat of, Lafayette County, Missouri. The population was 4,726 at the 2010 census. Located in western Missouri, Lexington lies approximately 40 miles (64 km) east of Kansas City and is part of the Greater Kansas City Metropolitan Area. It is the home of the Battle of Lexington State Historic Site, and of the former Wentworth Military Academy and College, which operated from 1880 to 2017.