Lucas Heights is a suburb in southern Sydney, in the state of New South Wales, Australia. It is located 31 kilometres south-west of the Sydney central business district, in the local government area of the Sutherland Shire. Lucas Heights is located on the Woronora River, which flows north into the Georges River.

Unusually for a suburb, Lucas Heights does not contain a residential area. The residential area previously part of Lucas Heights was renamed Barden Ridge in 1996 to increase the real estate value of the area, as it would no longer be instantly associated with the HIFAR nuclear reactor.

Lucas Heights was named after John Lucas Senior, a flour miller who in 1823 was granted 150 acres (0.6 km2) on the 'head of unnamed stream into Georges River'. He built a water-driven mill for grinding corn from the Illawarra farms. Small ships sailed up the coast into Botany Bay, Georges River and the Woronora River.