The Bangkok Mass Transit System, commonly known as the BTS or the Skytrain (Thai: รถไฟฟ้า rot fai fa), is an elevated rapid transit system in Bangkok, Thailand. It is operated by Bangkok Mass Transit System Public Company Limited (BTSC) under a concession granted by the Bangkok Metropolitan Administration (BMA). The system consists of 34 stations along two lines: the Sukhumvit Line running northwards and eastwards, terminating at Mo Chit and Bearing respectively, and the Silom Line which serves Silom and Sathon Roads, the central business district of Bangkok, terminating at the National Stadium and Bang Wa. The lines interchange at Siam Station and have a combined route length of 36.45 kilometers (22.65 mi). The system is formally known as the Elevated Train in Commemoration of HM the King's 6th Cycle Birthday (รถไฟฟ้าเฉลิมพระเกียรติ 6 รอบ พระชนมพรรษา).
Besides the BTS, Bangkok's rapid transit system includes the underground railway line MRT, and the elevated Suvarnabhumi Airport Link (SARL), serving several stations in the city before reaching the airport.