Abstract: A tensioning and damping element for chain drives, which comprises an elastically deformable ring part and a toothed rim arranged at the periphery thereof, the ring part being circular in the stress-free, uninstalled state and assuming, in the stressed, installed state, an ellipse-like shape between a non-loaded strand and a loaded strand of the chain drive, the toothed rim engaging with the non-loaded strand and the loaded strand and in so doing transmitting to the two strands a tensioning force which is caused by the ellipse-like deformation of the ring part. The ring part is constructed in such a manner that its cross-sectional profile steadily changes with increasing deformation of the ring part, in such a manner that the ratio of the height of the cross-sectional profile to the width of the cross-sectional profile in the maximally biased state of the ring part is at least 4% smaller than in the stress-free state of the ring part.