The 101 series (101系, 101-kei) was a DC electric multiple unit (EMU) commuter train type introduced in 1957 by Japanese National Railways (JNR), and formerly operated by East Japan Railway Company (JR East) and West Japan Railway Company (JR-West).

The last remaining trains were withdrawn in November 2003.

The prototype 101 series set was delivered in June 1957, as a 10-car (4+6-car) set classified as 90 series with all cars motored.

Production sets were delivered from March 1958, differing visually from the prototype in having exposed rain gutters along the top of each car.

A number of former 101 series trains were sold to the private railway operator Chichibu Railway in Saitama Prefecture in 1986, where they operated as 3-car 1000 series sets until March 2014.