|Etymology||William Pitt the Younger|
|State||New South Wales|
|Region||Greater Metropolitan Sydney|
|Municipality||Northern Beaches Council|
|⁃ location||north of Church Point|
|2nd source||Cahill Creek|
|⁃ location||Mona Vale|
|West Head and Barrenjoey Head|
|Length||10 km (6.2 mi)|
|Basin size||50.8 km2 (19.6 sq mi)|
|⁃ left||Bilgola Creek|
|⁃ right||McMahon's Creek, Careel Creek|
Pittwater is a semi–mature tide dominated drowned valley estuary, located about 40 kilometres (25 mi) north of the Sydney central business district, New South Wales, Australia; being one of the bodies of water that separate greater Metropolitan Sydney from the Central Coast.
Pittwater has its origin from the confluence of McCarrs Creek, to the west of Church Point and a number of smaller estuaries, the largest of which is Cahill Creek, that joins the Pittwater north of Mona Vale. The Pittwater is an open body of water, often considered a bay or harbour, that flows north towards its mouth into Broken Bay, between West Head and Barrenjoey Head, less than 1 kilometre (0.62 mi) from the Tasman Sea.
The total area of the Pittwater is 18.4 square kilometres (7.1 sq mi) and around ninety percent of the area is generally administered by the Hawkesbury–Nepean Catchment Management Authority, in conjunction with Northern Beaches Council.
The land adjacent to the Pittwater was occupied for many thousands of years by the Kuringgai peoples, an Aboriginal Australian grouping of uncertain origin. They used the river as an important source of food and a place for trade.
Pittwater extends from Mona Vale and Warriewood in the south, along the eastern ridge of the Barrenjoey Peninsula leading to Palm Beach and along the western ridge of the Lambert Peninsula leading to West Head. The eastern parts of the catchment are largely urbanised whilst the western parts are primarily Ku-ring-gai Chase National Park. Within the Pittwater lies Careel Bay, Refuge Cove, Saltpan Cove, Horseshoe Cove, Crystal Bay, McCarrs Creek, Browns Bay, Elvina Bay, Lovett Bay, Towlers Bay, Portuguese Bay, Coasters Retreat and The Basin. Scotland Island is located within the estuary.
The Kuringgai, often called Guringai, peoples were the traditional inhabitants of the land and waterways north of Sydney Harbour, through the Lane Cove River and across Broken Bay and beyond to Brisbane Water. Amongst the Kuringgai, there were many smaller units called clans, of which the Carigal were most prominent in the area surrounding Pittwater. During 1789 the impact of smallpox on aboriginal peoples led to extensive mortality, with the death rate estimated at somewhere between 50% and 90%. Conservatively, between 500 and 1000 Aboriginal people died on the coastal strip bounded by Botany Bay and Broken Bay. A significant proportion of these were Kuringgai.
The waterway was surveyed by crew members of HMS Sirius in 1788, and named Pitt Water after William Pitt the Younger, the then Prime Minister of Great Britain. The first regular water transport across Pittwater was the cutter Francis which carried set