Illawarra Harbour was the name of a port that was to have been constructed on Lake Illawarra in New South Wales, Australia. The port scheme commenced around 1888. The port was to have been developed by a company known as Illawarra Harbour and Land Corporation. A tender was accepted, in late 1892, and work commenced on a breakwater at the entrance of the lake at Windang, but that work ceased during the second half of 1893. In 1895, a railway was constructed on the western side of the lake. In 1898, a select committee hearing was told that the vast majority of shares in the company were in fact owned by an English-domiciled company, Illawarra Harbour and Railway Corporation. A planned dredged channel across Lake Illawarra and wharves on the company's land, at Elizabeth Point, near Tallawarra Point, were not constructed, no coal was ever shipped, and the mine and jetty scheme was abandoned in 1902.
The Illawarra Harbour and Land Corporation attempted to sell a sub-division of 288 allotments in 1897, without much success; land sales seem to have been closer to its real objective than was the establishment and operation of a port. The companies associated with the port scheme made some questionable related-party transactions involving directors of those companies. The only parts of the Illawarra Harbour port scheme that were ever used were some land, where the Dapto Smelting Works—a venture closely associated with the port scheme—was situated, after 1895, and the railway, after being connected to the smelter site and its sidings by another short railway line. The smelter closed, in 1905, due in part to the absence of a nearby port, which affected the feasibility of smelting low-grade ores.