St. Leonard is a census-designated place (CDP) in Calvert County, Maryland, United States.

The town has a volunteer fire department which has hosted numerous high-profile musical acts, including Lynyrd Skynyrd, Alan Jackson, and Hootie and the Blowfish at an outdoor pavilion adjacent to the fire department.

Notable places of interest near St. Leonard include Flag Ponds Nature Park, a nature preserve south of Long Beach along Chesapeake Bay, and Jefferson Patterson State Park 7 miles (11 km) south of town, home to an annual Celtic festival, to Maryland's state archaeological facility, and the site of several key naval battles fought in the Patuxent River during the War of 1812.

Maryland Routes 2/4 form the western side of the community, leading north 6 miles (10 km) to Prince Frederick, the Calvert County seat, and south 13 miles (21 km) to Solomons.

12.4% of all households were made up of individuals, and 4.7% had someone living alone who was 65 years of age or older.