Montgomery County is a county in the east central part of the U.S. state of Missouri. As of the 2020 census, the population was 11,322. Its county seat is Montgomery City. The county was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada.

Richard Montgomery was an Irish-born American military officer who first served in the British Army. He later became a major general in the Continental Army during the American Revolutionary War, and he is most famous for leading the unsuccessful 1775 invasion of northeastern Quebec.