Port Jackson, containing Sydney Harbour, is the natural harbour of Sydney, Australia. The harbour is an inlet of the South Pacific Ocean. Widely considered to be one of the world's finest harbours, it is known for its beauty, and in particular, as the location of the Sydney Opera House and Sydney Harbour Bridge. The location of the first European settlement in Australia, the harbour has continued to play a key role in the history and development of Sydney. The city itself lies on the southern shore, while the Northern Suburbs lie on the northern shore; which are linked by the Harbour Bridge. The Parramatta River forms the harbour's western arm.

Many recreational events are based on or around the harbour itself particularly the Sydney New Year's Eve celebrations and the starting point of the Sydney to Hobart yacht race.