The 209 series (209系) is an electric multiple unit (EMU) commuter train type operated by East Japan Railway Company (JR East) in the Tokyo area of Japan since 1993.
The 209 series was the first of the "New series trains" (新系列電車, Shin-keiretsu densha), and served as the basis for the E501, E217, 701, and E127 series rolling stock, as well as the succeeding E231 series stock. which in turn became the blueprint for successive trains developed by JR East and other railway companies in Japan.