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Copper (symbol Cu, atomic number 29) is a transition metal known for its reddish metallic luster and high electrical and thermal conductivity. It is malleable and ductile, with a face-centered cubic crystal structure. The metal melts at 1085°C and boils at 2562°C, and it resists corrosion in many environments owing to a protective patina of copper oxides and basic salts that forms when it is exposed to air.

Copper occurs in native form and in minerals such as chalcopyrite, bornite, and malachite. It is one of the most widely mined metals worldwide. It is typically refined by smelting and electrolytic refining. Recycled copper from scrap is a major source; copper is highly recyclable without loss of properties, and recycled metal generally requires less energy than primary production.

Major uses include electrical wiring and electronics, plumbing, heat exchangers, and corrosion-resistant equipment. Alloys such as brass (Cu-Zn) and bronze (Cu-Sn) extend its utility. Copper is also used for coins and as a protective coating on some architectural metals. It has antimicrobial properties and is an essential trace element for many organisms.

Natural copper consists mainly of two stable isotopes, 63Cu and 65Cu, with natural abundances of about 69% and 31% respectively. Copper forms diverse compounds, including oxides, sulfates, and halides. The symbol Cu is derived from cuprum, the Latin name for Cyprus, historically a major source of the metal.