The Calvert Peninsula is part of the Western Shore region of the U.S. state of Maryland. It extends about 25miles into Chesapeake Bay with the main bay providing its eastern border and the Patuxent River defining its western border. It constitutes a total land area of about 350sqmi and is essentially conterminous with Calvert County.
Immediately south of the Calvert Peninsula is the larger St. Mary's Peninsula, defined by the Patuxent and Potomac Rivers.
It is the site of Calvert Cliffs State Park and the Calvert Cliffs Nuclear Power Plant.