St. Leonard is a census-designated place (CDP) in Calvert County, Maryland, United States. The population was 742 at the 2010 census. Residents of the Calvert Beach and Long Beach communities also use the St. Leonard ZIP code designation. St. Leonard has a large antique dealer complex.
St. Leonard has a small central business district with several small shops, gas stations, and an independent grocery store originally owned and operated by former Calvert County Commissioner Patrick Buehler. An enclosed marketplace houses 80 vendors of antiques and collectibles.