Fort Denison, part of the Sydney Harbour National Park, is a protected national park that is a heritage-listed former penal site and defensive facility occupying a small island located north-east of the Royal Botanic Garden and approximately 1 kilometre (0.62 mi) east of the Opera House in Sydney Harbour, New South Wales, Australia. The island is also known as Mattewanye or Muddawahnyuh in the Eora language, and as Pinchgut Island.

The Sydney Harbour National Park is an Australian national park comprising parts of Port Jackson, Sydney and its foreshores and various islands. The 392-hectare (970-acre) national park lies in New South Wales and was created progressively, from 1975.