Lake Illawarra is located between the Illawarra escarpment and the Pacific Ocean on the NSW South Coast some 90 kilometres south of Sydney. Water flowing into it is both fresh (from the escarpment) and salty (from ocean tides).

The Lake is approximately 9.5 kilometres long and 5.5 kilometres wide, with an area of 33 square kilometres and a maximum depth of 3.7 metres. 13 boat ramps surround the lake and is a popular recreational location. The lake is a popular spot for fishing, prawning, and all water sports.

There is a boat and catamaran hire close by as well as several caravan parks. There is also a shared pathway that can be enjoyed by all.

Reddall Reserve on the foreshore of Lake Illawarra is a popular spot for picnics with its children's playground, amenities and kiosk.
The lake environment is administered by the Lake Illawarra Authority, a New South Wales statutory authority established pursuant to the Lake Illawarra Authority Act 1987 (NSW) with the aim of transforming the waters and foreshores of Lake Illawarra into an attractive recreational and tourist resource.

See also Lake Illawarra North 2, Lake Illawarra South 1 & 2
Please note that this is a multi-jurisdiction area,with most foreshore areas under either the Illawarra Lake Authority or Shellharbour City Council.