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.

Johann von Robais, Baron de Kalb, born Johann Kalb, was a Franconian-born French military officer who served as a major general in the Continental Army during the American Revolutionary War. He was mortally wounded while fighting against the British Army during the Battle of Camden.