Abstract: A protective-fire-hydrant-cover comprising an operating-nut-extender and a protective-fire-hydrant-casing. The operating-nut-extender is firmly coupled with an operating-nut of a fire-hydrant such that when the operating-nut-extender rotates, the operating-nut rotates therewith, the operating-nut-extender includes an inner-groove exhibiting a substantially circular shape. The protective-fire-hydrant casing includes a lock-mechanism therein, which includes a latch. The latch moves between at least a locked and un-operable position and an unlocked position. The protective-fire-hydrant-casing fits over the operating-nut-extender such that it covers the operating-nut-extender and the latch aligns with the groove. When the latch moves to locked and un-operable position the latch enters the inner-groove thus internally locking the protective fire-hydrant-casing with the operating-nut-extender thus locking the protective fire-hydrant-cover onto the fire-hydrant.