Sydney Harbour National Park, Nature reserve in Mosman Municipal Council, Australia.

Sydney Harbour National Park is a 392-hectare protected area of Port Jackson and its foreshores, gazetted in 1975 and managed by the NSW National Parks and Wildlife Service. It takes in Bradleys Head, Middle Head, Georges Head, Nielsen Park, Fort Denison, Goat Island, Shark Island, Clark Island, Rodd Island, Dobroyd Head, the Quarantine Station at North Head and The Gap bluff at South Head. About 40% of its land is heathland, 25% woodland and 15% eucalyptus forest.

The area was fortified in the 1800s with defensive structures built to guard the harbour from potential attacks. The remains of these military installations, including buildings and gun positions, still stand and reveal this period of colonial defence.

The park holds Guringai Resting Places at Reef Beach and the Quarantine Station, reburial sites where ancestral remains have been returned to Country; access is restricted at the Aboriginal community's request. At the Quarantine Station there are over a thousand engravings. The Eora, Guringai and Darug lived around the harbour before British colonisation, and by the mid-19th century they had been largely displaced from the Sydney area.

The reserve has several entry points, and visitors can choose different routes depending on what areas they wish to explore. Wearing good walking shoes and bringing water is advisable, especially on warm days when shade can be limited.

From vantage points throughout the reserve, visitors can spot whales during winter months as these marine mammals pass along the coast during their migration journey. This seasonal event offers a rare chance to witness large ocean creatures moving through their natural route.