The Antarctic tern (Sterna vittata) is a seabird in the family Laridae. It ranges throughout the southern oceans and is found on small islands around Antarctica as well as on the shores of the mainland. Its diet consists primarily of small fish and crustaceans. It is very similar in appearance to the closely related Arctic tern, but it is stockier, and it is in its breeding plumage in the southern summer, when the Arctic tern has shed old feathers to get its non-breeding plumage. The Antarctic tern does not migrate like the Arctic tern does, but it can still be found on a very large range. This tern species is actually more closely related to the South American tern.

Gulls, skuas and jaegers are the primary predators of the bird's eggs and young.

The Antarctic tern can be further divided into six subspecies. The total global population of this bird is around 140,000 individuals.

The Antarctic tern was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the other terns in the genus Sterna and coined the binomial name Sterna vittata. Gmelin based his description on the "wreathed tern" that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds . Latham had been provided with a specimen by the naturalist Joseph Banks. Latham mistakenly believed it had come from Christmas Island in the Indian Ocean but it had actually been collected at Christmas Harbour in the Kerguelen Islands in December 1776 during James Cook's third voyage to the Pacific Ocean. A drawing of the bird was made by William Wade Ellis. The genus name Sterna comes from the Old English word for a black tern. The specific epithet vittata is from Latin vittatus meaning "banded".

There are six recognized subspecies, each with their specific breeding sites.

Terns are in the family Laridae along with gulls and skimmers. Terns make up the sub-family Sterninae, which spreads into eleven genera. The Antarctic terns are in the genus Sterna, which has been established to be monophyletic. However, this claim has been challenged by a genetic study.

The Antarctic tern is a medium-sized tern ranging from 35 to 40 cm (14 to 16 in) in length with a wingspan of 74 to 79 cm (29 to 31 in). It weighs between 150 and 180 g (5.3 and 6.3 oz) but it tends to be heavier during the winter months.

In breeding plumage, the tern has light grey body and wings. Its deeply forked tail, lower back just above it and cheeks are white. It also has a distinctive black cap that reaches from the nape down to the bill and the eye is brownish-black. The bill, legs and feet are bright red. In non-breeding plumage, the black cap is reduced to just the area behind the eyes, the underparts become lighter and the bill becomes a dull reddish-black colour. Juveniles have yellowish-brown, grey, and white spots on their backs, with a yellowish-brown belly and breast. Their bill is dull black and the legs are dull red. The chicks have a yellowish-brown colour with black spots on their heads and back. They have a greyish white belly with a darker throat. The bill, legs and feet can be flesh colored or reddish black.