The mangrove killifish or mangrove rivulus, Kryptolebias marmoratus (syn. Rivulus marmoratus), is a species of killifish in the family Rivulidae. It lives in brackish and marine waters (less frequently in fresh water) along the coasts of Florida, through the Antilles, and along the eastern and northern Atlantic coasts of Mexico, Central America and South America (south to Brazil). It has a very wide tolerance of both salinity (0—68 ‰) and temperature (12–38 °C or 54–100 °F), 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.