The Odakyu 4000 series (小田急4000形, Odakyū 4000-gata) is a 1,500 V DC commuter electric multiple unit (EMU) train type operated by the private railway operator Odakyu Electric Railway in Japan since 2007.

[2] The trains are based on the JR East E233-2000 series narrow-body EMU design to permit subway running.

[2] The traction motors are fully enclosed to reduce environmental noise.

[3] The first train was delivered in May 2007, and the trains entered service in September 2007 on inter-running services between Odakyu and the Tokyo Metro Chiyoda Line, displacing 1000 series sets,[4] which were cascaded to surface lines to replace older 5000 and 5200 series sets.

From 26 March 2016, the 4000 series began operation on the JR East Joban Line.