Prince Frederick is an unincorporated community and census-designated place (CDP) in Calvert County, Maryland, United States.

In the War of 1812, Commodore Joshua Barney's Chesapeake Bay Flotilla found refuge from the advancing British in St. Leonard's Creek, several miles south of Prince Frederick, in June 1814.

While laying siege to Barney's force, the British under the command of Admiral Sir Alexander Cochrane plundered and destroyed the area nearby, including burning the town of Prince Frederick.

[9] In 1882, Prince Frederick burned a second time, when a massive fire destroyed virtually the entire town and its courthouse.

The project was to feature houses, a motel, shopping centers, a pier, a marina, beaches, and a clubhouse fronting the Chesapeake Bay.

Maryland Route 765 serves as Prince Frederick's Main Street and provides access to the courthouse and government center.

In the mid-1990s, a series of new loop roads and side streets were approved in Prince Frederick in order to divert local traffic off Route 2-4 and alleviate thru-traffic congestion.

A second portion of the road, Chesapeake Boulevard, opened in 2010 on the eastern side of Route 2-4 and provides access to the new Calvert Middle School.

On the western side of Prince Frederick, there is a large industrial park which attracted numerous businesses and places of commerce after offering free land sites.

Hallowing Point Park is a county-owned recreational area west of Prince Frederick which features tennis courts, athletic fields for baseball, softball, and soccer, and hiking and jogging trails.

Notable places in the Prince Frederick area include Battle Creek Cypress Swamp—a local nature preserve—and the Arthur Storer Planetarium, which is located on the grounds of Calvert High School.

Located on the southeastern side of town, there is a very large, triangular retention pond at the site of the Prince Frederick wastewater treatment plant.

[16] The plant's strange UFO-like appearance—approximately 500 feet (150 m) long per side and location in a secluded and heavily wooded area—in satellite imagery on Google Earth has evoked the curiosity of many locals, who have nicknamed the site the "Giant Triangle" and speculated on its purpose.

[17] Best-selling author Tom Clancy operated an insurance business in Prince Frederick prior to his literary career and was an active parishioner of St. John Vianney Catholic Church, and still owned a home near Prince Frederick on Chesapeake Bay until his death in 2013.

While on the faculty of Chesapeake Biological Laboratory in nearby Solomons, noted theoretical ecologist Dr. Robert Ulanowicz resided near Prince Frederick prior to his retirement in 2008.