Hydraulic rear axle steering mechanism for multi-axle vehicles, having a steering cylinder which comprises a cylinder chamber, a piston mounted in a sealing manner in the cylinder chamber, which piston divides the cylinder chamber into two working chambers (39, 40), and at least one piston rod supported by the piston, wherein the steering cylinder is provided with a mechanical blocking device (34, 35, 36, 36') which locks the piston once it reaches a central position within the steering cylinder, wherein the blocking device (34, 35, 36, 36') has at least one blocking member (36, 36') which in the blocked state is held by a locking element (34, 35) in an engaged position, and wherein the locking element (34, 35) is adjustable, by means of an actuator (37, 38, 45) which is actuated hydraulically and is separate from the piston and piston rod, between a blocking position in which the locking element (34, 35) holds the blocking member (36, 36') in the engaged position, and at least one first unblocking position in which the locking element (34, 35) releases the blocking member (36, 36'), characterised in that a return line from each of the two working chambers (39, 40) leads to a tank and a hydraulically unblockable valve (15, 17), in particular a load-holding valve, is arranged in each of the return lines, in that the hydraulically unblockable valves (15, 17) are designed as admission pressure-controlled valves whose control connection is connected in each case to a pressure line (11, 12) leading (34, 35, 36, 36') from a pump to the respective other working chamber (39, 40), and in that the hydraulically actuated actuator (37, 38, 45) is configured such that, when a first pressure value is applied, the locking element (34, 35) moves into the unblocking position and the admission pressure-controlled valves (15, 17) are configured such that, when a second pressure value is applied, they open at the control connection, wherein the second pressure value is higher than the first pressure value. having a steering cylinder which comprises a cylinder chamber, a piston mounted in a sealing manner in the cylinder chamber, which piston divides the cylinder chamber into two working chambers (39, 40), and at least one piston rod supported by the piston, wherein the steering cylinder is provided with a mechanical blocking device (34, 35, 36, 36') which locks the piston once it reaches a central position within the steering cylinder, wherein the blocking device (34, 35, 36, 36') has at least one blocking member (36, 36') which in the blocked state is held by a locking element (34, 35) in an engaged position, and wherein the locking element (34, 35) is adjustable, by means of an actuator (37, 38, 45) which is actuated hydraulically and is separate from the piston and piston rod, between a blocking position in which the locking element (34, 35) holds the blocking member (36, 36') in the engaged position, and at least one first unblocking position in which the locking element (34, 35) releases the blocking member (36, 36'), characterised in that a return line from each of the two working chambers (39, 40) leads to a tank and a hydraulically unblockable valve (15, 17), in particular a load-holding valve, is arranged in each of the return lines, in that the hydraulically unblockable valves (15, 17) are designed as admission pressure-controlled valves whose control connection is connected in each case to a pressure line (11, 12) leading (34, 35, 36, 36') from a pump to the respective other working chamber (39, 40), and in that the hydraulically actuated actuator (37, 38, 45) is configured such that, when a first pressure value is applied, the locking element (34, 35) moves into the unblocking position and the admission pressure-controlled valves (15, 17) are configured such that, when a second pressure value is applied, they open at the control connection, wherein the second pressure value is higher than the first pressure value.