A vehicle steering system, in which a steering member and steered wheels are not mechanically coupled to each other, includes a rotation angle restriction mechanism that restricts a rotation angle of the steering member within a restricted angular range. In a failure mode, that is, in a case where a malfunction occurs in a steering angle sensor, a steering direction is detected on the basis of a strain of the rotation angle restriction mechanism, which is detected by one of strain gauges at a corresponding one of a pair of terminal ends of a restricted angular range. Drive control is executed on a steered system actuator on the basis of the detected steering direction.