DeKalb County is a county located in the northwest portion of the U.S. state of Missouri. As of the 2020 census, the population was 11,029. Its county seat is Maysville. The county was organized February 25, 1845 and named for General Johann de Kalb, Baron de Kalb, of the Revolutionary War.

Maysville is a city in DeKalb County, Missouri, United States. The population was 1,095 at the 2020 census. Maysville is the county seat of DeKalb County.