Johnson County is a county located in western portion of the U.S. state of Missouri. As of the 2020 census, the population was 54,013. Its county seat is Warrensburg. The county was formed December 13, 1834, from Lafayette County and named for Vice President Richard Mentor Johnson.

Warrensburg is a city in and the county seat of Johnson County, Missouri, United States. The population was 20,313 at the 2020 census. The Warrensburg Micropolitan Statistical Area consists of Johnson County. The city is a college town as it is home to the University of Central Missouri.