Obelisk Beach, Nude beach in Mosman, Sydney, Australia

Obelisk Beach is a small sandy beach on the southern side of Middle Head in Mosman, within Sydney Harbour National Park. It faces Sydney Harbour and is backed by bushland where Aboriginal sites are found around Georges Head. The beach is part of Obelisk Bay.

Before 1788 the area around Georges Head was inhabited by Dharug-speaking Aboriginal people, and smallpox brought by colonists cut the Aboriginal population north of Sydney Harbour by up to 90% by 1795. In 1815 Governor Lachlan Macquarie gave Bungaree 15 acres on Georges Head and named him "Chief of the Broken Bay Tribe"; Bungaree kept a fishing boat on the beach with his family. In the early 20th century artists including Herbert Reginald Gallop painted the beach, which was also a popular picnic spot.

Obelisk Beach is a nude beach attended mainly by homosexual men and described as gay-friendly; before 2004 it was the site of a gay beat. Bungaree and his family kept a fishing boat on this beach, and in the early 20th century it was painted by artists such as Herbert Reginald Gallop and used for picnics.

Reaching the beach requires about ten minutes of walking through bushland from Chowder Bay Road, with limited parking available near the HMAS Penguin naval base. The path goes through natural vegetation, so sturdy footwear and staying on marked trails are important.

Bungaree, whom Governor Macquarie named "Chief of the Broken Bay Tribe" in 1815 and granted 15 acres on Georges Head, kept a fishing boat on this beach and fished from it with his family. The beach later served as a gay beat until 2004.