Cedar Hill is an unincorporated community and census-designated place (CDP) in Jefferson County, Missouri, United States. The population was 1,721 at the 2010 census.
A post office called Cedar Hill has been in operation since 1868. The community was named for cedar trees near the elevated town site.
Cedar Hill is located in northwestern Jefferson County at 38°21′22″N 90°38′30″W (38.356193, -90.641681). It is 32 miles (51 km) southwest of downtown St. Louis. Missouri Route 30, a four-lane highway, runs through the western side of the CDP, leading northeast into St. Louis and west 22 miles (35 km) to St. Clair.
According to the United States Census Bureau, the CDP has a total area of 2.3 square miles (5.9 km2), all land. The Big River, a northward-flowing tributary of the Meramec River, forms the southern and western limits of the CDP, and the community is the site of an old mill and dam.