A roller blind for a side window of a motor vehicle. The roller blind has a winding shaft, which is coupled via an articulated or flexible coupling mechanism to a spring drive situated outside the winding shaft. The winding shaft and the spring drive are accommodated inside a vertical window frame segment of a motor vehicle's window. The articulated or flexible coupling between the winding shaft and the spring drive makes it possible to approximate a curved path by means of two normally straight elements of the blind. Furthermore, a very flat characteristic tension curve can be achieved for the spring drive, even when the winding shaft is very short.