The Long-tailed Skua, Stercorarius longicaudus, is a seabird in the skua family Stercorariidae.

This is the smallest of the skuas at about 38cm length, excluding the elongated central tail feathers of the summer adult, which can add another 20cm or so.

This species breeds in the high Arctic of Eurasia and North America, with major populations in Russia, Alaska and Canada and smaller populations around the rest of the Arctic. It nests on dry tundra or higher fells. It is a migrant, wintering in the south Atlantic and Pacific. Passage juvenile birds sometimes hunt small prey in ploughed fields or golf-courses, and are typically quite fearless of humans.

This bird feeds mainly on lemmings, and numbers fluctuate with the food supply. On migration, Long-tailed Skuas are more likely to catch their own food, and less likely to steal from gulls and terns than larger species.

This species is unmistakable as an adult, with grey back, dark primary wing feathers without a white "flash", black cap and very long tail. Adults often hover over their breeding territories.

Juveniles are much more problematic, and are difficult to separate from Arctic Skua over the sea. They are slimmer, longer-winged and more tern-like than that species, but show the same wide range of plumage variation. However, they are usually colder toned than Arctic, with greyer shades, rather than brown.