Bismuth is a chemical element that has atomic number 83 and has been given the chemical symbol Bi. Bismuth, a trivalent poor metal, resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead, and brittle, with a silvery white color, and often a pink tinge owing to the surface oxide.

Bismuth metal has been known from ancient times, although until the 18th century it was often confused with lead and tin, which each have some of the metal's physical properties. The name possibly comes from German words meaning "white mass."

Bismuth is the most naturally diamagnetic of all metals, and only mercury has a lower thermal conductivity.

Bismuth has classically been considered to be the heaviest naturally-occurring stable element. Recently, however, it has been found to be very slightly radioactive: its only naturally occurring isotope bismuth-209 decays via alpha decay into thallium-205 with a half-life of more than a billion times the estimated age of the universe.

Bismuth compounds are used in cosmetics, medicines, and in medical procedures. Bismuth has unusually low toxicity for a heavy metal. As the toxicity of lead has become more apparent in recent years, alloy uses for bismuth metal, as a replacement for lead, have become an increasing part of bismuth's commercial importance.