碳（Carbon，拉丁文意为煤炭）是一种化学元素，符号为C，原子序数为6，位于元素周期表中的IV A族，属于非金属。每个碳原子有四颗能够进行键合的电子，因此其化合价通常为4。自然产生的碳由三种同位素组成：C和C为稳定同位素，而C则具放射性，其半衰期约为5,730年。碳是少数几个自远古就被发现的元素之一（见化学元素发现年表）。

碳的同素异形体有数种，最常见的包括：石墨、钻石及无定形碳。这些同素异形体之间的物理性质，包括外表、硬度、电导率等等，都具有极大的差异。在正常条件下，钻石、碳纳米管和石墨烯的热导率是已知材质中最高的。

Carbon (from Latin:carbo "coal") is a chemical element with symbol C and atomic number 6. On the periodic table, it is the first (row 2) of six elements in column (group) 14, which have in common the composition of their outer electron shell. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. Three isotopes occur naturally, C and C being stable while C is radioactive, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.