The origins of the Mass Rapid Transit (MRT) are derived from a forecast by city planners in 1967 which stated the need for a rail-based urban transport system by 1992. Following a debate on whether a bus-only system would be more cost-effective, then Minister for Communications Ong Teng Cheong, came to the conclusion that an all-bus system would be inadequate, as it would have to compete for road space in a land-scarce country.
The network was built in stages, with the North South line given priority because it passed through the Central Area that has a high demand for public transport. The Mass Rapid Transit Corporation (MRTC)—later renamed SMRT Corporation—was established on 14 October 1983; it took over the roles and responsibilities (which was the construction and operation the MRT system) of the former provisional Mass Rapid Transit Authority. On 7 November 1987, the first section of the North South Line started operations, consisting of five stations over six kilometres. Fifteen more stations were opened later, and the MRT system was officially launched on 12 March 1988 by then Prime Minister Lee Kuan Yew. Another 21 stations have been added to the system; the opening of Boon Lay on the East West Line on 6 July 1990 marked the completion of the system two years ahead of schedule.
The MRT has since been expanded. The first expansion was in 1996, a S$1.2 billion expansion of the North South Line into Woodlands, merging the Branch line into the North South line and joining Yishun and Choa Chu Kang stations. The concept of having rail lines that bring people almost directly to their homes led to the introduction of the Light Rail Transit (LRT) lines connecting with the MRT network. On 6 November 1999, the first LRT trains on the Bukit Panjang LRT went into operation. In 2002, the Changi Airport and Expo stations were added to the MRT network. The North East line, the first line operated by SBS Transit, opened on 20 June 2003, one of the first fully automated heavy rail lines in the world. On 15 January 2006, after intense two-and-a-half years lobbying by the public, Buangkok station was opened. On 20 June 2011, Woodleigh station was opened. The Boon Lay Extension of the East West line, consisting of Pioneer and Joo Koon stations, opened on 28 February 2009. The Circle line opened in four stages from 28 May 2009 to 14 January 2012. Stage 1 of Downtown line opened on 22 December 2013 with its official opening made on 21 December 2013 by Prime Minister Lee Hsien Loong. Stage 2 opened on 27 December 2015, after being officially opened on 26 December by Prime Minister Lee. The Tuas West Extension of the East West line, consisting of Gul Circle, Tuas Crescent, Tuas West Road, and Tuas Link stations, opened on 18 June 2017. Stage 3, the final stage of Downtown line, opened on 21 October 2017 with its official opening made on 20 October 2017 by Coordinating Minister for Infrastructure and Minister for Transport Khaw Boon Wan.