Abstract: There is disclosed herein a fire hydrant protection device which prevents unauthorized individuals from tampering with or operating fire hydrants. In one form the protection device provides an outlet cap member provided with a projection suitable for engagement by a special wrench such as for removal or installation of the cap and a cover member movably associated therewith which includes provisions preventing access to the cap member projection by conventional tools thus insuring that only authorized individuals will be able to remove the device. In another form, the device is designed to be installed over the valve actuating mechanism so as to similarly prevent access thereto by individuals not having the special wrench.