Aswitchableandtunableytterbium-dopedfiberringlaser(YDFL)isreportedanddemonstrated.EmployingaSagnacloopmirrorfabricatedbyan85-cm-longpolarization-maintainingfiber(PMF),theproposedYDFLcanoperatewithstabledual-wavelengthlasingortunablesingle-wavelengthlasingaround1064nm.Bothstabledual-wavelengthlasingandtunablesingle-wavelengthlasingareachievedbyadjustingapolarizationcontrollerintheSagnacloopmirror.Theexperimentalresultsshowthattheoutputoftheproposedfiberlaserwithtwodifferentoperationmodesisratherstableatroomtemperature.