Mortdale is a suburb located in southern Sydney, in the state of New South Wales, Australia. Mortdale is located 20 kilometres south of the Sydney central business district and is part of the St George area. Mortdale is situated in the local government area of Georges River Council. Mortdale extends south to Lime Kiln Bay, on the Georges River. Mortdale Heights is a locality in the western corner of the suburb.

Southern Sydney is the southern metropolitan area of Greater Sydney, in the state of New South Wales, Australia.