The 123 series (123系, Hyaku-nijūsan-kei) is a single-car electric multiple unit (EMU) train type introduced in 1986 by Japanese National Railways (JNR), and later operated by East Japan Railway Company (JR East), Central Japan Railway Company (JR Central), and West Japan Railway Company (JR-West).
The 123 series was created in 1986 from former KuMoNi 143 baggage cars which had become surplus to requirements. Some units were also converted from KuMoYuNi 147 postal cars (123-40 series, later 123-5000 series), and from KuMoYa 143 tractor cars (123-600 series).
As of 1 April 2012, one 123 series car (KuMoHa 123-1) is operated by JR East, based at Matsumoto Depot for use on the Chuo Main Line and Shinonoi Line. Five 123 series cars (KuMoHa 123-2 to 6) are operated by JR-West on the Ube Line, Onoda Line, and Sanyo Main Line.
This car was converted from former baggage car KuMoNi 143-1 at Nagano Works in October 1986. It was reliveried in March 1990 following conversion to wanman driver only operation.
These three cars were converted in February 1987 at Hiroshima Works from former baggage cars KuMoNi 143-2, 3, and 6, respectively, originally for use on the Kabe Line. The two original pantographs were replaced with one PS16J lozenge-type pantograph at the No. 1 end.
These two cars were converted in April 1987 at Suita Works from former baggage cars KuMoNi 143-7 and 8, respectively, originally for use on Hanwa Line branch services. The original pantographs at the No. 1 end were removed on conversion.
These cars were converted in January 1987.
These two cars were converted in March 1988 by JR Central at Hamamatsu Works from former tractor cars KuMoYa 143-601 and 602, respectively, for use on the Minobu Line. These cars had gangway doors at the ends, three sliding doors per side, and two pantographs. Inverter-controlled air-conditioning was added in December 1988.
These cars were modified in June 1989 at Hamamatsu Works by JR Central from earlier KuMoHa 123-40 series cars, with the addition of inverter-controlled air-conditioning.
These cars were modified by JR Central from earlier KuMoHa 123-40 and KuMoHa 123-5040 series cars, for use on wanman driver only operation services on the Minobu Line. Gangway doors were also added on conversion.
The last remaining 123 series car operated by JR East was withdrawn from the start of the revised timetable on 15 March 2013, with operations replaced by E127 series two-car EMUs.