The Onkaparinga River runs from its source between Mount Torrens and Charleston in the Mount Lofty Ranges, and flows south westerly to an estuary at Port Noarlunga. The catchment is over 500 km² in area, and is in part located in the Onkaparinga River National Park.
The Onkaparinga River is the second major river of the Adelaide region, after the River Torrens. The name derives from the Indigenous Kaurna name Ngangiparri which translates as "The Women's River". In 1837 William Light named it Field's River, or the Field River, after Lieut William George Field RN (1804-1850) of the brig Rapid, who carried out the first surveys in the vicinity, but Governor George Gawler soon reinstated the Indigenous name.