K Train or simply K may refer to:
K (Broadway Brooklyn Local), earlier KK, discontinued in 1976 K (Eighth Avenue Local), replaced the AA in 1985 and merged into the C in 1988 K Ingleside, Muni Metro line serving the West Portal and Ingleside neighborhoods K Line (Los Angeles Metro), a light rail line in Los Angeles County, California MTR Rotem EMU, rolling stock on the Hong Kong MTR often referred to as "K-Train"