The river between Wisemans Ferry and the Pacific Ocean marks the boundary of Greater Metropolitan Sydney in the south and the Central Coast region to the north.

Secondary tributaries include Brisbane Water and Pittwater, which, together with the Hawkesbury River, flow into Broken Bay and thence into the Tasman Sea north of Barrenjoey Head.

The land adjacent to the Hawkesbury River was occupied by Aboriginal peoples: the Darkinjung, Darug, Eora, and Kuringgai.

Once formed, the Hawkesbury River proper flows generally northwards, albeit with a significant number of meanders.

In the area around Brooklyn the river is crossed by the major road and rail services that follow the coast north from Sydney.

Despite forming the effective boundary of the metropolitan region of Sydney for its entire length, there are very few fixed crossings of the Hawkesbury River proper.

Boats would wait in the protection of Broken Bay and Pittwater, until favourable weather allowed them to make the ocean journey to Sydney Heads.

With the opening of the railway from Sydney to Windsor in 1864, farm produce could be shipped upriver for onward transportation by train.

[21][22] In May 2017, the New South Wales state government released the Hawkesbury-Nepean Valley Flood Risk Management Strategy,[23] that proposed raising the height of Warragamba Dam by an additional 17 metres, using the Climate Change Mitigation Fund.

[citation needed] Activists also claim that the raising of the dam wall will give rise to additional developments downstream, which are currently not allowed to build on floodplains with a risk of a one-in-hundred-year flood.

They also claim that any raising of the dam wall will be ineffective at flood mitigation, as the Warragamba River only contributes around 15% of water volume to the Hawkesbury-Nepean system.

This is especially true in the lower reaches of the river, where the steep and rugged terrain inhibits road construction.

[30][31] The Australian leg of the Red Bull Cliff Diving World Series takes place in Hawkesbury.

Windsor and also Dargle ski park on the Hawkesbury river each year hold a Circuit Boat race meeting with boats travelling from all over country According to the Hawkesbury Nepean Catchment Management Authority, the Hawkesbury River estuary supports the second-largest commercial coastal fishery of estuary prawns, oysters (prior to the outbreak of QX disease) and fish in New South Wales, with a wholesale value of $6.3 million annually.