Cape Henlopen State Park is a Delaware state park on 5,450 acres (2,210 ha) on Cape Henlopen in Sussex County, Delaware, United States. William Penn made the beaches of Cape Henlopen one of the first public lands established in what has become the United States in 1682 with the declaration that Cape Henlopen would be for "the usage of the citizens of Lewes and Sussex County." Cape Henlopen State Park has a 24-hour and year-round fishing pier as well as campgrounds. The remainder of the park is only open from sunrise to sunset, and includes a bathhouse on the Atlantic Ocean, an area for surf-fishing, a disc golf course, and bicycle and walking paths. The beach at Herring Point is a popular surfing spot. The park is a stop on Delaware's Coastal Heritage Greenway.

Cape Henlopen, on Delaware Bay, has long been a public use area although it did not officially become a Delaware state park until 1964. William Penn, the founder of Pennsylvania and early leader of Delaware, decreed that Cape Henlopen and its natural resources be set aside for the use and enjoyment of the citizens of the Delaware Colony. Penn's decree established Cape Henlopen as one of the first public use parcels of land in the Thirteen Colonies.

The cape was an important strategic location for the U.S. Navy and Army during the American Revolution, War of 1812, Civil War, World War I, and World War II. Cape Henlopen Light, the sixth lighthouse built on the Atlantic Coast, was constructed from 1767-1769. This lighthouse was in operation until 1924 when it was abandoned after it was extensively damaged in 1920 by a storm. The lighthouse now rests at the bottom of the Atlantic Ocean, after falling into the water on April 13, 1926.

A small gun platform was built by 1918 near the present site of Point Comfort parking lot. It was abandoned and removed prior to construction of Fort Miles.

During World War II, the U.S. Army built Fort Miles at Cape Henlopen. Numerous bunkers, concrete observation towers and the pier built to accommodate the laying of mines on the harbor floor remain today. Within the park grounds are a handful of fire control towers from that era, as well as underground gun batteries (bunkers) which were to be used in conjunction with the towers against the eventuality of air attack. Off the coast on the bay side are two lighthouses: the Harbor of Refuge Light and the Delaware Breakwater East End Light.

Cape Henlopen State Park is home to a vast array of wildlife, notably several species of shorebird. The black skimmer, least tern, and piping plover are all endangered species that are abundant within the park. Horseshoe crabs are also very common, especially in the Delaware Bay.

The beach at Cape Henlopen State Park is open year-round. There are two beaches that are open to swimming at the park with lifeguard patrols between the Memorial and Labor Day weekends. A modern bath house with showers, changing rooms and a snack bar is located at the northern beach. North Shore Beach, the southern beach at Cape Henlopen State Park, is a popular beach among lesbians.

Cape Henlopen State Park has two facilities that are rented out for large group gatherings, a pavilion for picnics and the "Officer's Club" a remnant of the Fort Miles days. The 18 hole disc golf course and basketball courts are open year-round. Hunting is permitted during Delaware's designated hunting seasons in some parts of the park.