象牙是一种白色硬质物体。主要成分为牙本质，和骨头的成分相似。狭义地说是雄性的亚洲象、非洲象、猛犸象的獠牙，广义地也可以指河马、野猪、海象、鲸等动物的獠牙或牙齿。

象牙在古代是一种贵重的材料，用来制作牙雕、假牙、扇子、骰子等。近代用来做装饰品或用具，如牙雕、台球、骰子、钢琴键、麻将、扣子等。塑料出现之后，在众多领域替代了象牙，但因为象牙的稀有，一些奢侈品仍然使用象牙。

由于大象数量锐减，环保主义者希望在国际范围禁止象牙贸易。不过是否应该禁止象牙贸易则直到今天还存在争议。

Ivory is a hard, white material from the tusks (traditionally elephant's) and teeth of animals, that can be used in art or manufacturing. It consists mainly of dentine (inorganic formula Ca₁₀(PO₄)₆(CO₃)·H₂O)), one of the physical structures of teeth and tusks. The chemical structure of the teeth and tusks of mammals is the same, regardless of the species of origin. The trade in certain teeth and tusks other than elephant is well established and widespread; therefore, "ivory" can correctly be used to describe any mammalian teeth or tusks of commercial interest which are large enough to be carved or scrimshawed. It has been valued since ancient times for making a range of items, from ivory carvings to false teeth, fans, and dominoes. Elephant ivory is the most important source, but ivory from mammoth, walrus, hippopotamus, sperm whale, killer whale, narwhal and wart hog are used as well. Elk also have two ivory teeth, which are believed to be the remnants of tusks from their ancestors.