The Waterfall rail accident was a train accident that occurred on 31 January 2003 near Waterfall, New South Wales, Australia. The train derailed, killing seven people aboard, including the train driver. The accident is famously remembered by systems engineers due to the poorly designed safety systems.

Waterfall is a small suburb in southern Sydney, in the state of New South Wales, Australia. It is 40 kilometres south of the Sydney central business district in the Sutherland Shire. It is the southernmost suburb of Sydney in the eastern corridor, on the Princes Highway, bordering Helensburgh.