A vehicle seat longitudinal adjuster (2) includes two guide rail pairs (P1, P2) with a first guide rail (3) and a second guide rail (4) movable with respect to the first guide rail, a motor unit (12), a gear unit (G) with a gear rotary shaft (6) connected to the first guide rail and a rotatable gear element (7). A transmission unit (11) is coupled with the gear unit and the motor unit to transmit torque to the gear rotary shaft. A gearbox (9) receives the gear unit. A support (5) receives the gearbox inside a gap (BR) formed between the guide rails and passes through a second rail opening (13) and extends out of the guide rail opening and closes the second rail opening. A vehicle seat (1), has the longitudinal adjuster for mechanically and longitudinally adjusting the vehicle seat.