钚（Plutonium，中国大陆及港澳译作钚）是原子序数为94、元素符号为Pu的放射性超铀元素。它属于锕系金属，外表呈银白色，接触空气后容易锈蚀、氧化，在表面生成无光泽的二氧化钚。钚有六种同素异形体和四种氧化态，易和碳、卤素、氮、硅起化学反应。钚暴露在潮湿的空气中时会产生氧化物和氢化物，其体积最大可膨胀70%，屑状的钚能自燃。它也是一种放射性毒物，会于骨髓中富集。因此，操作、处理钚元素具有一定的危险性。

钚是天然存在于自然界中的质量最重的元素。它最稳定的同位素是钚-244，半衰期约为八千万年，足够使钚以微量存在于自然环境中。

Plutonium is a transuranic radioactive chemical element with symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon and hydrogen. When exposed to moist air, it forms oxides and hydrides that expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous.