The Parramatta River is an intermediate tide-dominated, drowned valley estuary[2] located in Sydney, New South Wales, Australia.

With an average depth of 5.1 metres (17 ft),[3] the Parramatta River is the main tributary of Sydney Harbour, a branch of Port Jackson.

[1][7] The river was formed 15 to 29 million years ago as its waters began to cut a valley into sandstone and shale.

Waterways flowing into the Parramatta River, west–to–east include:[6] From its start at the confluence of Toongabbie Creek and Darling Mills Creek at North Parramatta, the river flows in a southerly direction through the grounds of Cumberland Hospital.

Both banks are largely open to the public, with parkland and walkways, downstream to James Ruse Drive.

The whole of Sydney Harbour including its tributary rivers is subject to a long range Catchment Management Plan.

The New South Wales Government has a documented policy in relation to access to the harbour and river foreshores, including public access to intertidal lands where landowners have absolute waterfronts but where the waterfront is exposed at low tide.

13 councils sit within the Parramatta River catchment group and all have committed to tackling the two major polluters: sewer overflows and stormwater.

Since settlement, the river and the harbour have presented a formidable barrier between the early–European settled southern Farm Cove precinct, to development north of the waterway.

(Putney Punt) Until 1970 the river was an open drain for Sydney's industry and consequently the southern central embayments are contaminated with a range of heavy metals and chemicals.

The main contaminated areas of the Parramatta River are: Water quality is monitored by the Office of Environment and Heritage (New South Wales) (OEH) for faecal coliforms and e. coli, but only as far west as Cabarita.

Many areas of the river, particularly the swampy heads of bays, have been reclaimed, often being used as rubbish dumps before being converted into playing fields.

The former AGL site has been analysed, a remediation plan developed and approved, remediation completed and construction commenced on medium to high density residential development, but the sediments, which independent research shows to be contaminated with pollutants from the AGL operations, have not yet had the investigation stage finalised (as of 2000[update]).

Most rowing training is done in the middle to upper reaches of the river between Abbotsford and Homebush Bay because there is less water traffic and therefore less waves and more protection from wind.

Where there is no foreshore access, cycleways are routed through quiet residential streets with clearly marked sections of the road reserved for cyclists.