The South American tern (Sterna hirundinacea) is a species of tern found in coastal regions of southern South America, including the Falkland Islands, ranging north to Peru (Pacific coast) and Brazil (Atlantic coast).

Its breeding range extends on the Atlantic coast from east central Brazil southwards through Argentina and the Falkland Islands to Tierra del Fuego.

It nests on islands, beaches and cliff tops, and when not breeding may be seen offshore, in estuaries and harbours.

A very large number of birds were nesting in an area about 130 square metres (150 sq yd).

These were smaller than the eggs of the Sandwich tern but resembled them in general appearance, though every one was differently marked.