Casula is a suburb of Sydney, in the state of New South Wales, Australia. It is 34 kilometres south-west of the Sydney central business district, in the local government area of the City of Liverpool. Casula is the first suburb immediately south of Liverpool on the Hume Highway and the Main Southern railway line between Sydney and Melbourne. Casula consists of undulating, gently rolling land, with elevations across the suburb being mostly between 30 and 70 metres above sea level.