Single-frequency　output　power　of　12　W　at　1064　nm　is　demonstrated.　Pumped　by　a　fiber-coupled　diode　laser,　the　Nd:YVO4　produces　58.6%　of　the　slope　efficiency　with　respect　to　absorbed　pump　power,　and　52.7%　of　the　optical-optical　efficiency　and　nearly　diffraction-limited　output　with　a　beam　quality　parameter　of　M-2　approximate　to　1.11.　To　the　best　of　our　knowledge,　this　is　the　highest　slope　efficiency　and　optical-optical　efficiency　in　single-frequency　Nd:YVO4　ring　laser.　The　slope　efficiency　of　the　single　frequency　laser　is　close　to　the　limit　of　the　efficiency.　[GRAPHICS]　output　spectrum　of　the　single-frequency　Nd:YVO4　ring　laser　(C)　2010　by　Astro　Ltd.　Published　exclusively　by　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA