A longitudinal adjuster (10), for a vehicle seat (1), includes at least one pair of rails (12), formed from a lower seat rail (14a) and an upper seat rail (14b). The seat rails mutually engage around each other and are movable relative to each other in a longitudinal direction (x) and are lockable to each other by a locking device (16). The locking device has at least one latching plate (18), which is movable in the vertical direction (z). The latching plate has a guide pin (20) protruding in the vertical direction. The upper seat rail has an opening (22) aligned with the guide pin. A guide sleeve (24) extends into a cavity between the seat rails and is accommodated in the opening. The guide pin is guided by the guide sleeve. The upper seat rail and the guide sleeve are connectable by a bayonet catch.