The swallow-tailed gull (Creagrus furcatus) is an equatorial seabird in the gull family, Laridae. It is the only species in the genus Creagrus. It spends most of its life flying and hunting over the open ocean. The main breeding location is in the Galápagos Islands, particularly the rocky shores and cliffs of Hood, Tower and Wolf Islands, with lower numbers on most of the other islands. It is more common on the eastern islands where the water is warmer.
It is the only fully nocturnal gull and seabird in the world, preying on squid and small fish which rise to the surface at night to feed on plankton.