The Seibu 20000 series (西武20000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. First introduced in 2000, a total of eight 10-car sets and eight 8-car sets were built between 1999 and 2005 by Hitachi for use on Seibu Ikebukuro Line and Seibu Shinjuku Line services.