The Sm4 electric multiple unit (EMU) is a low-floor train used by the VR Group for longer-distance Helsinki commuter rail services.

The Spanish company CAF was contracted to manufacture the units, based on a design by Fiat Ferroviaria (later acquired by Alstom).

The Sm4 passenger compartments are fitted with air conditioning, CCTV cameras and display screens that can be used to show e.g. route information.

[4] The units have partly low floors with all of the entrances at platform level, and they are equipped with toilets accessible to the disabled.

The new Sm5 low floor trains that started to enter commercial service in November 2009 have completely replaced the Sm4 units on HSL commuter rail routes.