Suin may refer to:

Korean rail lines

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  • Suin Line (1937–1945), a narrow gauge line of the Chōsen Railway in Gyeonggi Province
  • Suin Line, a metro line of the Seoul Metropolitan Subway serving the Seoul Capital Area, active 2012–2020
  • Suin–Bundang Line, a commuter rail service of the Seoul Metropolitan Subway system, opened in 2020