A wheel hub drive unit comprising: a wheel hub; a wheel hub bearing which is arranged in a wheel rim and on the central axis of the wheel hub and comprises an inner bearing ring and an outer bearing ring; a housing which encloses the wheel hub bearing and forms a housing space, the housing space comprising a first receiving chamber sealed against the external environment and comprising a second receiving chamber sealed against the external environment; a drive device which is arranged within the first receiving chamber; and a reduction transmission which is arranged in the second receiving chamber; wherein the inner bearing ring is a rotating ring and is connected via a first connecting part to the output end of the reduction transmission and to the wheel hub, the outer bearing ring is a non-rotating ring and is connected to the housing, and the input end of the reduction transmission is connected to the output end of the drive device, wherein the first connecting part comprises a connecting shaft and an annular part connected thereto, wherein the connecting shaft is connected to the inner bearing ring by means of fitting; and the annular part is arranged coaxially to the connecting shaft and is connected to the output end of the reduction transmission and the wheel hub, wherein the outer diameter of the annular part is greater than the outer diameter of the connecting shaft, wherein the annular part is arranged opposite the housing in the axial direction and acts as a side wall of the second receiving chamber, and the outer circumferential surface of the connecting shaft, the output end of the drive device and the inner circumferential surface of the housing enclose the second receiving chamber and wherein the annular part is connected to the output end of the reduction transmission, in that a plurality of first protrusions are arranged on the annular part, which protrusions protrude towards the output end of the reduction transmission and which are distributed along the circumferential direction with intermediate spaces, and in that a plurality of second protrusions are arranged on the output end of the reduction transmission, which protrusions protrude towards the connecting shaft and are distributed along the circumferential direction with intermediate spaces, wherein each first protrusion is clamped between two adjacent second protrusions and/or each second protrusion is clamped between two adjacent first protrusions. a wheel hub; a wheel hub bearing which is arranged in a wheel rim and on the central axis of the wheel hub and comprises an inner bearing ring and an outer bearing ring; a housing which encloses the wheel hub bearing and forms a housing space, the housing space comprising a first receiving chamber sealed against the external environment and comprising a second receiving chamber sealed against the external environment; a drive device which is arranged within the first receiving chamber; and a reduction transmission which is arranged in the second receiving chamber; wherein the inner bearing ring is a rotating ring and is connected via a first connecting part to the output end of the reduction transmission and to the wheel hub, the outer bearing ring is a non-rotating ring and is connected to the housing, and the input end of the reduction transmission is connected to the output end of the drive device, wherein the first connecting part comprises a connecting shaft and an annular part connected thereto, wherein the connecting shaft is connected to the inner bearing ring by means of fitting; and the annular part is arranged coaxially to the connecting shaft and is connected to the output end of the reduction transmission and the wheel hub, wherein the outer diameter of the annular part is greater than the outer diameter of the connecting shaft, wherein the annular part is arranged opposite the housing in the axial direction and acts as a side wall of the second receiving chamber, and the outer circumferential surface of the connecting shaft, the output end of the drive device and the inner circumferential surface of the housing enclose the second receiving chamber and wherein the annular part is connected to the output end of the reduction transmission, in that a plurality of first protrusions are arranged on the annular part, which protrusions protrude towards the output end of the reduction transmission and which are distributed along the circumferential direction with intermediate spaces, and in that a plurality of second protrusions are arranged on the output end of the reduction transmission, which protrusions protrude towards the connecting shaft and are distributed along the circumferential direction with intermediate spaces, wherein each first protrusion is clamped between two adjacent second protrusions and/or each second protrusion is clamped between two adjacent first protrusions.