铱是一种化学元素，符号为Ir，原子序为77，属于铂系过渡金属，为质地坚硬易碎的银白色固体。铱是所有元素中密度第二高的元素（仅次于锇），而其耐腐蚀性是所有金属元素中最高的，在2000℃高温下仍然能抵抗腐蚀。虽然固态铱只能被少数熔融盐和卤素侵蚀，但是铱粉末则相比之下较容易发生化学反应，可以燃烧。

1803年，史密森·特南特在自然铂矿石的不可溶杂质中发现了铱元素。由于该元素的盐有众多鲜艳的颜色，所以他根据希腊神话中的彩虹女神伊里斯（Iris）把这一新元素命名为「Iridium」。铱是地球地壳中最稀有的元素之一。其全球年产量及年消耗量只有三吨。自然存在的铱有Ir和Ir两种同位素，后者的丰度较高。铱的其他同位素都是不稳定同位素。

Iridium is a chemical element with symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, iridium is generally credited with being the second densest element (after osmium) based on measured density, although calculations involving the space lattices of the elements show that iridium is denser. It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable.