Abstract: A shaft decoupler wherein driving and driven components having grooved fles are keyed together by rollers held in the grooves by lands between recesses of a retaining assembly that normally rotates with the mentioned components and is momentarily arrested to allow the driving and driven components to advance the roller carrying grooves to alignment with the recesses to effect decoupling. The decoupler is characterized by the use of high strength plastic rollers, cooperating indexing elements to limit relative rotation between the driving component and the retaining assembly, and a solid lubricant filled plastic thrust and journal bearing.