Motor vehicle rear seat

A motor vehicle rear seat (1) has two units (4), which are set side by side along a horizontal axis, are each provided with a respective squab and a respective backrest (9) and are arranged on opposite sides of a support device (12) having a lower base (13) designed to be fastened to a floorpan of the motor vehicle; the device (12) has a body (21) that supports the two units (4) and has a position that can be adjusted in a longitudinal direction and in height with respect to the lower base (13); a fixing device (34) is provided to block this body (21) in the desired position with respect to the lower base (13).