Lemay is an unincorporated community and census-designated place (CDP) in south St. Louis County, Missouri, United States.

[4] Lemay was named after Francois Lemai, who operated a ferry boat across the Meramec River in the early nineteenth century.

At the 2000 census there were 17,215 people, 7,186 households, and 4,390 families living in the CDP.

There were 7,580 housing units at an average density of 1,743.2 per square mile (673.1/km2).

The racial makeup of the CDP was 98.51% White, 0.02% African American, 0.007% Native American, 0.53% Asian, 0.01% Pacific Islander, 0.66% from other races, and 0.96% from two or more races.