An actuator lock for selectively limiting the movements of a linear actuator comprising an axially fixed lock shaft having a splined portion rotatable into and out of alignment with a correspondingly splined portion on the axially movable part of the actuator. When the splined portions on the lock shaft and axially movable part are in proper alignment with each other, the axially movable part is free to move axially relative to the lock shaft, but when the lock shaft is rotated so that the splined portions are out of alignment with each other, axial movement is limited to the axial clearance between the ends of the splined portions. The relative locations and lengths of the splined portions on the lock shaft and movable part of the actuator determine the lock positions and extent of permissible axial movement when the lock shaft is rotated to a locking position.