A safety sleeve for exposed rotating shafts, in particular, for cylindrical shafts with smooth outer surfaces. The safety sleeve includes an enclosure member that substantially encloses the exposed shaft. The enclosure member is mounted to the shaft in releasable driving engagement with a mounting member which is firmly secured to the shaft. The enclosure member is normally rotatably driven by the mounting member, but when there is external contact with the enclosure member the enclosure member is released from driving engagement with the mounting member so that the enclosure member remains stationary while the mounting member rotates with the shaft in sliding contact with the enclosure member. In the preferred embodiment the enclosure member is tubular and the mounting member is a pair of annular collars.