The Lochaber Narrow Gauge Railway was a 3 ft (914 mm) narrow gauge industrial railway. It was a relatively long line, built for the construction and subsequent maintenance of a 15 miles (24 km) long tunnel from Loch Treig to a factory near Fort William in Scotland. The tunnel was excavated to carry water for the Lochaber hydro-electric power scheme in connection with aluminium production by the British Aluminium Company.