Aratus pisonii, commonly known as the mangrove tree crab, is a species of crab which lives in mangrove trees in tropical and subtropical parts of the Americas, from Florida to Brazil on the Atlantic coast, and from Nicaragua to Peru on the Pacific coast. It feeds mostly on the leaves of the mangroves, but is an omnivore, and prefers animal matter when possible. A. pisonii is the only species in the monotypic genus Aratus.