The mangrove rivulus or mangrove killifish, Kryptolebias marmoratus, is a species of killifish in the family Rivulidae. It lives in brackish and marine waters along the coasts of Florida, through the Antilles, and along the eastern and northern Atlantic coasts of Mexico, Central America and South America. It has a very wide tolerance of both salinity and temperature, can survive for about two months on land, and mostly breeds by self-fertilization. It is typically found in areas with red mangrove and sometimes lives in burrows of Cardisoma guanhumi crabs.

Amphibious fish are fish that are able to leave water for extended periods of time. About 11 distantly related genera of fish are considered amphibious. This suggests that many fish genera independently evolved amphibious traits, a process known as convergent evolution. These fish use a range of terrestrial locomotory modes, such as lateral undulation, tripod-like walking, and jumping. Many of these locomotory modes incorporate multiple combinations of pectoral-, pelvic-, and tail-fin movement.