MARS (マルス Marusu), which stands for MAgnetic electronic seat Reservation System or, more recently, Multi Access seat Reservation System, is a train ticket reservation system used by the railway companies of Japan Railways Group (JR Group) and travel agencies in Japan.
The host of the system is located in Kokubunji, Tokyo and managed by Railway Information Systems Co., Ltd. (JR Systems), a JR Group company jointly owned by the seven members of the group.
Ticket windows at JR stations equipped with MARS terminals are called Midori no Madoguchi (みどりの窓口, literally "green window"), which sell tickets for all JR Group trains with reserved seats beginning one month prior to the ride.