Illowra Battery, Military fortification in Port Kembla, Australia.

Illowra Battery is a coastal defense complex in Port Kembla consisting of two gun emplacements connected by underground tunnels with concrete stairs and metal trolley tracks. The structure spans multiple levels and uses both natural cavities and artificially excavated passages.

Construction of Illowra Battery began in late 1941 and was completed in February 1942, with two emplacements for British BL 6-inch Mk. XI guns. Their protective gun-shields came from the decommissioned World War I-era cruisers HMAS Brisbane, Sydney and Melbourne. The battery was abandoned shortly after the end of World War II in 1945.

The battery's name comes from Illowra, the Aboriginal name for Hill 60, whose shoreline below the bunkers was used by Aboriginal Australians as a commercial fishing ground. Visitors today see graffiti on the concrete, such as "PETER" and "CANTAL" on the outer face and "Teigan" with a drawn face inside the tunnels.

Access to the tunnels is through the lower parking area, but bring a flashlight or head lamp since the underground passages are dark. Wear sturdy footwear and be prepared for damp and potentially slippery surfaces.

The battery was abandoned in 1945, and a mushroom farm was later set up in its main bunker, where the cool temperature and humidity suited edible fungi. The site is now visited by urban explorers, whose graffiti covers the concrete, including the names "PETER" and "CANTAL" and the words "BUCK" and "PAHELP" on the top beam.