Singapore rail system mainly consists of a passenger urban rail transit system spanning the entire city-state: a rapid transit system collectively known as the Mass Rapid Transit (MRT) system operated by the two biggest public transport operators SMRT Trains (SMRT Corporation) and SBS Transit, as well as several Light Rail Transit (LRT) rubber-tyred automated guideway transit lines also operated by both companies. In addition, local specialised light rail lines are in operation in places such as the Singapore Changi Airport and Sentosa.
Although Singapore is not a member of the International Union of Railways (UIC) given the nature of Singapore as a city-state and its lack of a national railway proper, SMRT Corporation, SBS Transit and the Land Transport Authority are members of the International Association of Public Transport (UITP). SMRT Corporation is also a member of the Community of Metros (CoMET) benchmarking group.
Singapore proposed Two international rail links to Malaysia to replace the KTM railway. The Johor Bahru-Singapore Rapid Transit System is currently under construction and is scheduled to begin operations in 2026.
Mass Rapid Transit (MRT) : The Mass Rapid Transit, which opened in 1987, is a heavy rail metro system that serves as the major backbone of Singapore's public transport system along with public buses; as of 2021, the network has a length of 216 km (134.22 mi) and 187 stations. The Land Transport Authority plans to provide a more comprehensive rail transport system by expanding the rail system to a total of 360 km (223.69 mi) by the year 2030, with eight in ten households living within a 10-minute walking distance of an MRT station.
The current MRT network consists of six main lines: the North South Line, East West Line, Circle Line and Thomson–East Coast Line operated by SMRT Trains (SMRT Corporation) and the North East Line and Downtown Line operated by SBS Transit. Two more lines, the Jurong Region Line and the Cross Island Line, will open in stages from 2026 and 2029 respectively.
Light Rail Transit (LRT) : In several new towns, automated rubber-tyred light rail transit systems function as feeders to the main MRT network in lieu of feeder buses. The first LRT line, which is operated by SMRT Light Rail, opened in Bukit Panjang in 1999 to provide a connection to Choa Chu Kang in neighbouring Choa Chu Kang New Town. Although subsequently hit by over 50 incidents, some of which resulted in several days of system suspension, similar systems albeit from a different company were introduced in Sengkang and Punggol in 2003 and 2005 respectively, both operated by SBS Transit.
Changi Airport, the main international airport of Singapore, is served by an automated rubber-tyred Skytrain system which first opened in 1990 to connect both the landside and airside of Terminals 1 and 2 when the latter terminal opened the same year.
Historically Singapore had also operated several industrial railways at the Port of Singapore and the Mandai Quarry and several military railways at military bases at Admiralty and Changi.