The is a DC electric multiple unit (EMU) commuter train type operated by West Japan Railway Company (JR-West) in the Kansai Region of Japan.
The 321 series was developed from the earlier 207 series to replace the ageing 201 series and 205 series trains on the Tà Âkaidà  Main Line. One 321 series set also replaced the 207 series (set Z16) withdrawn due to collision damage sustained in the Amagasaki derailment of 25 April 2005.
The 321 series share the same assignments as their 207 series counterparts. All 39 sets are allocated to Aboshi depot.
KuMoHa 321 and MoHa 321 cars each have two scissors-type pantographs.