Lake St. Clair or Lake Saint Clair[2] is an unincorporated community and census-designated place (CDP) in Franklin County, Missouri, United States.

It is in the southeast part of the county, surrounding a lake impounded on a tributary of Hoosier Creek, a south-flowing tributary of the Meramec River.

The community is bordered to the north by the city of Saint Clair and is 54 miles (87 km) southwest of St. Louis.

Lake St. Clair was first listed as a CDP prior to the 2020 census.

This Franklin County, Missouri state location article is a stub.