The roseate tern (Sterna dougallii) is a species of tern in the family Laridae. The genus name Sterna is derived from Old English "stearn", "tern", and the specific dougallii refers to Scottish physician and collector Dr Peter McDougall (1777–1814). "Roseate" refers to the bird's pink breast in breeding plumage.

English naturalist George Montagu described the roseate tern in 1813. Genetically, it is most closely related to the white-fronted tern (S. striata), with their common ancestor a sister lineage to the black-naped tern (S. sumatrana).

This species has a number of geographical subspecies, differing mainly in bill colour and minor plumage details.

S. d. dougallii breeds on the Atlantic coasts of Europe and North America, and winters south to the Caribbean and west Africa. Both the European and North American populations have been in long-term decline, though active conservation measures have reversed the decline in the last few years at some colonies, most notably at Rockabill Island off the coast of Dublin, Ireland, which now holds most of the European population (about 1200 pairs). The tropical forms S. d. korustes and S. d. bangsi are resident breeders from east Africa across the Indian Ocean to Japan. They have more red on the bill. The long-billed and short-winged S. d. gracilis breeds in Australia and New Caledonia. The north-western Indian Ocean holds populations of S. d. arideensis. Some authors suggest that only three subspecies, nominate S. d. dougallii, S. d. arideensis, and S. d. gracilis, should be retained.

This is a small-medium tern, 33–36 cm (13–14 in) long with a 67–76 cm (26–30 in) wingspan, which can be confused with the common tern, Arctic tern, and the larger, but similarly plumaged, Sandwich tern. The thin sharp bill is black, with a red base which develops through the breeding season, and is more extensive (to fully red) in the tropical and southern hemisphere subspecies. It is shorter-winged and has faster wing beats than common or Arctic tern. The upper wings are pale grey and its under parts white, and this tern looks very pale in flight, like a small Sandwich tern, although the outermost primary flight feathers darken during the summer. The adults have very long, flexible tail streamers and orange-red legs. In summer, the underparts of adults take on the pinkish tinge which gives this bird its name.

In winter, the forehead becomes white and the bill black. Juvenile roseate terns have a scaly appearance like juvenile Sandwich Terns, but a fuller black cap than that species.

As with other Sterna terns, roseate tern feeds by plunge-diving for fish, almost invariably from the sea; it is much more marine than allied terns, only rarely visiting freshwater lagoons on the coast to bathe and not fishing in fresh water. It usually dives directly, and not from the "stepped-hover" favoured by Arctic tern. The offering of fish by the male to the female is part of the courtship display.

Unusual for a tern, the roseate tern shows some kleptoparasitic behaviour, stealing fish from other seabirds, at British colonies most often from puffins. This habit greatly increases their food-collecting ability during bad weather when fish swim deeper, out of reach of plunge-diving terns, but still within reach of the deeper-diving Puffins.