The water buffalo (Bubalus bubalis), also called the domestic water buffalo or Asian water buffalo, is a large bovid originating in the Indian subcontinent and Southeast Asia. Today, it is also found in Europe, Australia, North America, South America and some African countries. Two extant types of water buffalo are recognized, based on morphological and behavioural criteria: the river buffalo of the Indian subcontinent and further west to the Balkans, Egypt and Italy and the swamp buffalo, found from Assam in the west through Southeast Asia to the Yangtze valley of China in the east.

The wild water buffalo (Bubalus arnee) most likely represents the ancestor of the domestic water buffalo. Results of a phylogenetic study indicate that the river-type water buffalo probably originated in western India and was domesticated about 6,300 years ago, whereas the swamp-type originated independently from Mainland Southeast Asia and was domesticated about 3,000 to 7,000 years ago. The river buffalo dispersed west as far as Egypt, the Balkans, and Italy; while swamp buffalo dispersed to the rest of Southeast Asia and up to the Yangtze River valley.

Water buffaloes were traded from the Indus Valley civilisation to Mesopotamia, in modern Iraq, 2500 BC by the Meluhhas. The seal of a scribe employed by an Akkadian king shows the sacrifice of water buffaloes.

Water buffaloes are especially suitable for tilling rice fields, and their milk is richer in fat and protein than that of dairy cattle. A large feral population became established in northern Australia in the late 19th century, and there are smaller feral herds in Papua New Guinea, Tunisia and northeastern Argentina. Feral herds are also present in New Britain, New Ireland, Irian Jaya, Colombia, Guyana, Suriname, Brazil, and Uruguay.