Abstract: A fire hose coupling locking device is disclosed which effectively secures a twist-type, high-pressure, quick-connect fire hose coupling from twisting loose when pressure is applied. Typically, it is permanently attached to a friction knob or lug at the top of a collar on the high-pressure outlet side on the fire pumper. It is pivotable about the lug and of sufficient length to span the coupling faces of the high-pressure outlet side to the fire hose and to engage of engaging the friction knob or lug on the top of the collar on the fire hose. Any relative rotation of the collars when water under high pressure is initially forced through the coupling is prevented.