A vehicle steering system including: (a) a steering operation member; (b) a movement-amount variably transmitting device including: (b-1) a housing fixed to a vehicle body; (b-2) a differential mechanism including (i) a first element connected to the steering operation member, (ii) a second element movable relative to the first element, and (iii) a third element engaged with the first and second elements; and (b-3) a drive source for moving the third element, such that an amount of relative movement of the first and second elements is changeable depending on an amount of movement of the third element; and (c) a wheel turning device connected to the second element to turn a vehicle wheel. The movement-amount variably transmitting device further includes (b-4) a third-element-movement inhibiting device for inhibiting movement of the third element. The steering system further includes (d) a third-element-movement inhibition cancelling device for cancelling inhibition of the movement of the third element.