A slag pit is a designated area or pit where slag, a byproduct of metal smelting or refining processes, is disposed of or stored. Slag is the non-metallic material that remains after the desired metal has been extracted from ore during the smelting process. It consists of various impurities and waste materials that are separated from the metal.

In a slag pit, the molten slag is poured or directed into the pit, where it solidifies and cools down. Over time, the accumulated slag may be further processed or recycled for various industrial applications, such as construction aggregate, road base material, or as a component in cement production. Slag pits are commonly found in steel mills, foundries, and other metal processing facilities where metal smelting and refining operations take place.