The 117 series is a Japanese suburban electric multiple unit (EMU) train type introduced in 1979 by Japanese National Railways (JNR), and currently operated by West Japan Railway Company (JR-West). The train type was operated by Central Japan Railway Company from 1987 until 2013. A total of 216 cars were manufactured. When JNR was privatized and divided into the individual JR Group companies, JR Central received 72 cars, while JR-West took possession of 144.

The San'yō Main Line is a major railway line owned by JR Group companies in western Japan, connecting Kōbe Station and Moji Station, largely paralleling the coast of the Seto Inland Sea, in other words, the southern coast of western Honshu. The San'yō Shinkansen line largely parallels its route. The name Sanyō derived from the ancient region and highway San'yōdō, the road on the sunny (south) side of the mountains.