The MRT Sungai Buloh–Serdang–Putrajaya line will be the twelfth rail transit line, the fourth fully automated and driverless rail system in Klang Valley area. It is a part of the larger rail transport system in Kuala Lumpur known as Greater KL/Klang Valley Integrated Transit System. The line is numbered 12 and coloured gold on transit map.
It is one of three planned rail lines under Klang Valley Mass Rapid Transit Project by MRT Corp. The Phase 1 between Kwasa Damansara and Kampung Batu expected to be operational by July 2021. The remaining line is expected to be operational in 2022.
The approved rail alignment is 52.2km in length, of which 13.5km is underground. A total of 37 stations, 11 of them underground, will be built. The line will stretch from Sungai Buloh to Putrajaya and will include densely populated areas Sri Damansara, Kepong, Batu, Jalan Sultan Azlan Shah, Jalan Tun Razak, KLCC, Tun Razak Exchange, Kuchai Lama, Seri Kembangan and Cyberjaya. It is expected to have a ridership of 533,000 passengers per day once completed.