皇帝蟹，又名帝王蟹、石蟹、白石蟹或岩蟹，即石蟹科的甲壳类，它们主要分布在寒冷的海域。由于它们的体型巨大及肉质美味，很多物种都被广泛捕捉来作为食物，当中最为普遍的是堪察加拟石蟹。因全球暖化，帝王蟹正成为入侵物种。

一般相信皇帝蟹是源自像寄居蟹的祖先，故成年的皇帝蟹并不对称。皇帝蟹腹部的不对称与寄居蟹的相似，都是装入螺旋形的壳中。以往皇帝蟹与寄居蟹都一同分类在寄居蟹总科，但皇帝蟹现已和软腹蟹科（Hapalogastridae）一同被分类到独立的石蟹总科内。

King crabs are a superfamily of crab-like decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab, Paralithodes camtschaticus.