Cedar Beach, Coastal beach in Mount Sinai, United States.

Cedar Beach is a coastal area in Mount Sinai featuring two separate sections with sandy shores along Long Island Sound. Each section offers its own character and facilities, making them distinct destinations within the beach complex.

In the mid-19th century the harbor mouth lay to the east and the peninsula was reached from Port Jefferson; when tides and winds closed it, a new opening on the west side shifted access to Miller Place. During the Revolutionary War Major Benjamin Tallmadge and his Continental dragoons landed here before marching via Pipestave Hollow to burn the British stronghold at Manor St. George; the route is now the Benjamin Tallmadge Historic Trail. Dredging in Mount Sinai Harbor continued until the 1960s.

Cedar Beach has drawn visitors since the Long Island Rail Road reached neighbouring Port Jefferson in 1873, and Marilyn Monroe and Arthur Miller spent time here in the 1950s. The Cedar Beach Nature Center in the nature preserve behind the beachfront holds hands-on exhibits on the local marine life. Travelling carnivals occasionally set up in the parking lot.

Cedar Beach sits at the end of a peninsula reached by road from Miller Place, with the main parking areas near the eastern entrance by Cedar Beach Main. A paved walkway runs through the nature preserve behind the beachfront, linking the main section to Cedar Beach West and its fishing pier, boat launch ramp and marina.

The peninsula was once joined to Port Jefferson; when tides and winds closed Mount Sinai Harbor's eastern mouth, a new opening on the west side shifted its connection to Miller Place. Dredging in the harbor continued until the 1960s.