The 103 series (103系, 103-kei) is a DC electric multiple unit (EMU) commuter train type introduced in 1963 by Japanese National Railways (JNR), and currently operated by West Japan Railway Company (JR West) and Kyushu Railway Company (JR Kyushu). They were also operated by East Japan Railway Company (JR East) and Central Japan Railway Company (JR Central).

Some former JR East sets were also sold for second hand use in Indonesia, where they operated on the KRL Jabodetabek system in Jakarta between 2004 and 2016.

JR East has previously operated a large number of 103 series sets on the following lines.

A single four-car 103 series set remained in use by JR East on the Senseki Line in the Sendai area between November 2006 up until 21 October 2009.

JR Central has formerly used 103 series sets on Chuo Main Line services in the Nagoya area, but these were subsequently replaced by 211 series and 313 series trains.

JR-West continues to operate a large number of 103 series sets, many of which have received extensive life-extension refurbishment. JR-West currently operates 103 series sets on the following lines. They were also used on the Osaka Loop Line until October 2017. As of 2024, there are 63 cars still in service.

Previous Operations (JR West):

JR Kyushu operated a fleet of nine 6-car 103 series sets on JR Chikuhi Line inter-running services onto the Fukuoka City Subway Kūkō Line beginning in 1982.^{[unreliable source?]}