The Seibu 401 series (西武401系) is an electric multiple unit (EMU) train type operated by the private railway operator Seibu Railway on commuter services in the Tokyo area of Japan from 1978 to 1997.

401 series train sets were transferred to Sangi Railway in 1990.

Among other Seibu EMUs sent to that railway, it's the only 2-car EMU series on Sangi Railway line.

The 800 and 820 series conversion included modifications of the trains, so that they won't make contact with the station platforms.

[2] This Japanese rail transport related article is a stub.