A fire spanner, also commonly known as a hydrant wrench, is a specialized hand tool carried by firefighters for operating fire hydrants and connecting hose couplings.

Its primary function is to turn the pentagonal or square operating nut on a hydrant to open or close the water supply. The tool typically features a head with a socket designed to fit these specific nuts.

In addition to hydrant operation, the spanner is an essential multi-tool. The head often includes a slot or lug used to pry and tighten the rocker lugs on hose couplings, ensuring a secure connection. Its flat, sturdy body can also be used as a prying tool to force open doors or windows. Typically made of drop-forged steel or aluminum for strength and durability, the fire spanner is a compact but vital piece of equipment carried on every fire apparatus.