水豚（学名：Hydrochoerus hydrochaeris）是水豚属下仅存的两种生物之一。它是一种半水栖的食草动物，也是世界上体型最大的啮齿类动物。原产于南美洲智利以外的稀树草原和丛林中。

水豚是高度社会化的动物，最大的水豚群数量可达100头，但一般在10至20头之间。虽然因其肉及毛皮有利用价值而遭到捕猎，但该物种依然无危。其种加词hydrochaeris和属名一样，都是来自希腊语ὕδωρ（hydor ：水）和χοίρος（choiros：猪）。

The capybara (Hydrochoerus hydrochaeris) is a large rodent of the genus Hydrochoerus of which the only other extant member is the lesser capybara (Hydrochoerus isthmius). The capybara is the largest rodent in the world. Close relatives are guinea pigs and rock cavies, and it is more distantly related to the agouti, chinchillas, and the coypu. Native to South America, the capybara inhabits savannas and dense forests and lives near bodies of water. It is a highly social species and can be found in groups as large as 100 individuals, but usually lives in groups of 10–20 individuals. The capybara is not a threatened species and is hunted for its meat and hide and also for a grease from its thick fatty skin which is used in the pharmaceutical trade.