Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al₂SiO₄(F,OH)₂. It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple.

Although it is often associated with golden yellow and blue, it comes in a variety of colors, including colorless. The rarest are natural pinks, reds, and delicate golden oranges, sometimes with pink hues.

Topaz is a nesosilicate mineral. It is one of the hardest naturally occurring minerals and has a relatively low index of refraction. It occurs in many places in the world.