2100 series may refer to the following Japanese train types:
Chikuho Electric Railroad 2100 series electric multiple unit operated on the Chikuhō Electric Railroad Line Ichibata Electric Railway 2100 series EMU Izukyū Corporation 2100 series EMU Iyotetsu 2100 series streetcar Kanto Railway KiHa 2100 series DMU Keikyu 2100 series EMU, introduced in 1998 Keisei 2100 series EMU; see Nagano Electric Railway 2100 series EMU, introduced in 2011 Odakyu 2100 series EMU, see Odakyu 2000 series