, 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.
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.