The North South line (NSL) is a Mass Rapid Transit (MRT) line in Singapore, operated by SMRT. Coloured red on the rail map, the line is 45 kilometres (28 mi) long and serves 27 stations, 11 of which, between the Bishan and Marina South Pier stations, are underground. It runs from Jurong East station, located in western Singapore, to Marina South Pier station in the Central Area, via Woodlands station in northern Singapore. All the trains on the NSL run with a six-car formation.
It is the first MRT line to be built in Singapore, with the first section from Yio Chu Kang station to Toa Payoh station beginning service on 7 November 1987, followed by an extension southwards to Raffles Place station on 12 December the same year and northwards to Yishun station on 20 December 1988. After the southern extension to Marina Bay station on 4 November 1989, the North South line was formed and split from the East West line. In the 1990s, the line extended to the north and west connecting to the Branch line via Woodlands through the Woodlands line extension.