Refractory brick, also known as fire brick, is a type of specialized brick which is designed for use in high heat environments such as kilns and furnaces. Numerous companies manufacture refractory brick in a range of shapes, sizes, and styles, and it can be ordered directly through manufacturers or through companies which supply materials to people who work with high heat processing of materials. High quality refractory brick has a number of traits which make it distinct from other types of brick.

The primarily important property of refractory brick is that it can withstand very high temperatures without failing. It also tends to have low thermal conductivity, which is designed to make operating environments safer and more efficient. Furthermore, refractory brick can withstand impact from objects inside a high heat environment, and it can contain minor explosions which may occur during the heating process. It may be dense or porous, depending on the design and the intended utility.

This brick product is made with specialty clays which can be blended with materials such as magnesia, silicon carbide, alumina, silica, and chromium oxide. The exact composition of refractory brick varies, depending on the applications it is designed for, with manufacturers disclosing the concentrations of ingredients and recommended applications in their catalogs. Using refractory brick which is not designed for the application can be dangerous, as the bricks may fail, cracking, exploding, or developing other problems during use which could pose a threat to safety in addition to fouling a project.