A guided-wave rotating retarder has been developed. The device is based on the generation of a rotating elasto-optics effect by the contemporary application of three 120-degrees space-phased and time-phased forces. A first experiment made by using a GRIN lens is reported. A retarder with 1 radian of magnitude is obtained which can rotate 180 degrees. The magnitude and the rotation of the device axis are continuously adjustable. The device can be exploited also for fiber-optic components and it constitutes the basis for endless polarization compensators.