The E131 series (E131系) is a DC electric multiple unit (EMU) train type operated by the East Japan Railway Company. It began operations in the Chiba area on 13 March 2021, on the Sagami Line on 18 November 2021, and on the Nikkō Line and the Utsunomiya Line on 12 March 2022. The trains are equipped for driver-only operation.

The Sagami Line is a railway line in Kanagawa Prefecture, Japan, operated by East Japan Railway Company. It approximately parallels the east bank of the Sagami River. The line connects Hashimoto Station in Sagamihara and Chigasaki Station in Chigasaki.