Festus is a city in Jefferson County, Missouri, United States. The population was 11,367 at the 2009 estimated census. Festus and its neighbor Crystal City are often collectively known as the "Twin Cities"; however, they are incorporated separately.
Festus is located at 38°13′10″N 90°24′3″W / 38.21944°N 90.40083°W / 38.21944; -90.40083 (38.219490, -90.400936).
According to the United States Census Bureau, the city has a total area of 4.8 square miles (12.4 km²), all of it land.