河马（学名：Hippopotamus amphibius）的名字源自于希腊语「ιπποπόταμος」（英文名称即hippopotamus，希腊语的hippos即「马」，potamus即「河」），英文常缩写成「hippo」，是非洲的大型草食性哺乳类动物，是生物分类法里河马科中的两个延伸物种的其中一个（另一个是倭河马）。

河马外型浑圆可爱，但事实上攻击性甚强，是非洲最危险的动物之一，为杀人最多的草食性哺乳动物，也是陆上体型第三大动物。然而，河马牙、肉等价值珍贵，导致盗猎问题严重，目前已成为易危物种。

The common hippopotamus (Hippopotamus amphibius), or hippo, is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae, the other being the pygmy hippopotamus (Choeropsis liberiensis or Hexaprotodon liberiensis). The name comes from the ancient Greek for "river horse" (ἱπποπόταμος). After the elephant and rhinoceros, the common hippopotamus is the third-largest type of land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, the closest living relatives of the Hippopotamidae are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago.