Redonda Island, Island in Beagle Channel, Tierra del Fuego, Argentina.

Redonda Island is a small island of about 50 hectares at the mouth of Lapataia Bay in the Beagle Channel, with a maximum length of 1,022 m and width of 840 m. It is a former rocky nunatak polished by ice from a glacier that descended from the Darwin Range during the Quaternary glaciations. Its shores are bordered by Magellanic forests and underwater kelp beds of giant cachiyuyo.

In 1971 Argentina and Chile agreed to submit the sovereignty of the Beagle Channel islands to an arbitral tribunal, which was to announce its ruling to Queen Elizabeth II of England. The dispute concerned the 1881 boundary treaty: some Chilean interpretations held that the binational limit ended on the southern coast of Isla Grande de Tierra del Fuego, which would have made all the channel's waters and islands Chilean and left Argentina with a dry coast. Redonda Island's status as Argentine territory was confirmed after this long border dispute.

On the island operates Argentina's southernmost postal unit, so visitors often send a postcard or letter from there. A Prefectura Naval outpost on the island was built by prisoners from the Ushuaia jail, and walkers can see it along the trail to the western tip.

Boats leave from the Puerto Guaraní pier in Ensenada Zaratiegui bay, on the Beagle Channel shore of Tierra del Fuego National Park, and circle the island before landing. A trail leads to the western tip, where viewpoints look over Argentine and Chilean islands. Services run from spring until mid-April; the crossing is exposed, so dress for wind and possible summer snow.

Redonda Island runs Argentina's southernmost postal unit, where visitors often mail a postcard. The Prefectura Naval outpost on the island was built by inmates of the Ushuaia prison. Divers can explore rock walls dropping 27 metres, lined with kelp forests.