Illawong is a suburb in southern Sydney, in the state of New South Wales, Australia. Illawong is located 27 kilometres south of the Sydney Central Business District, in the local government area of the Sutherland Shire in the area commonly called Menai. The post code is 2234, which is also assigned to the contiguous suburbs of Menai, Bangor Barden Ridge and Alfords Point. Illawong sits between the southern shore of the Georges River and the northern shore of the Woronora River.