A furnace is a device used for high-temperature heating. It is a container that is heated to a very high temperature, so that substances that are put inside it, such as metal, will melt or burn.

The name derives from Latin word fornax, which means oven. The heat energy to fuel a furnace may be supplied directly by fuel combustion, by electricity such as the electric arc furnace, or through induction heating in induction furnaces.

In metallurgy, several specialized furnaces are used. These include:

Furnaces used in smelters, including:

• The blast furnace, used to reduce iron ore to pig iron

Steelmaking furnaces, including:

• Puddling furnace
• Reverberatory furnace
• Bessemer converter
• Open hearth furnace
• Basic oxygen furnace
• Electric arc furnace
• Electric induction furnace

Furnaces used to remelt metal in foundries.

Furnaces used to reheat and heat treat metal for use in:

• Rolling mills, including tinplate works and slitting mills.
• Forges