Disclosed is a hydraulic steering system (100) for a vehicle, especially a mobile working machine, comprising at least two steering cylinders (1, 2) within which two cylinder pistons (3, 4) can be displaced, and a first hydraulic pump (14) that can be adjusted regarding the swept volume. The position or the direction of displacement of the cylinder pistons (3, 4) in the steering cylinders (3, 4) defines the steering angle or the steering direction of the steerable vehicle wheels relative to a body (5) of the vehicle. The displaceable cylinder pistons (3, 4) divide the associated steering cylinder (1, 2) into two respective pressure chambers (6 and 7, 8 and 9). The first connection (46) of the adjustable hydraulic pump (14) is joined to one of the pressure chambers (6 or 7, 8 or 9) of the two steering cylinders (1, 2) according to the steering direction while the second connection (15) thereof is joined to the other respective pressure chamber (6 or 7, 8 or 9) of the two steering cylinders (1, 2) in a closed circuit.