The Tristan albatross (Diomedea dabbenena) is a large seabird from the albatross family. One of the great albatrosses of the genus Diomedea, it was only widely recognised as a full species in 1998.

Albatrosses belong to the family Diomedeidae of the order Procellariiformes, along with shearwaters, petrels, storm petrels, and diving petrels. They share certain identifying features. First, they have nasal passages that attach to the upper bill called naricorns, although the nostrils on the albatross are on the sides of the bill. The bills of Procellariiformes are also unique in that they are split into between 7 and 9 horny plates. Albatrosses also produce a stomach oil made up of wax esters and triglycerides that is stored in the proventriculus. This is used against predators as well as an energy rich food source for chicks and for the adults during their long flights.

While not all scientists believe it is a full species with some retaining it as a subspecies of the wandering albatross (now the snowy albatross), a 2004 study of the mitochondrial DNA of the wandering albatross species complex supported the split. Other studies have shown it to be the most genetically distinct member of the wandering albatross species complex. This may be due to it diverging from their common ancestor before all its relatives, or because it underwent particularly strong genetic drift. Among the major experts, BirdLife International has split this species,

Diomedea refers to Diomedes, whose companions turned to birds. The epitheton dabbenena refers to Roberto Dabbene, an Italian-Argentine ornithologist.

The Tristan albatross is practically indistinguishable from the snowy albatross at sea but is smaller and has a slightly darker back. It is 110 cm (43 in) from beak to tail and has a wingspan of up to 3.05 m (10.0 ft). The Tristan albatross also never attains the full white plumage of the snowy albatross, and its bill is about 25 mm (0.98 in) shorter.

Due to the difficulty in distinguishing them from snowy albatrosses, their distribution at sea is still not fully known, but the use of satellite tracking has shown that they forage widely in the South Atlantic, with males foraging west of the breeding islands towards South America and females to the east towards Africa. There have been sightings near Brazil and also off the coast of Australia.

Tristan albatrosses are endemic to the islands of the Tristan da Cunha group and more specifically Gough Island. The majority of the world's population nest on Gough Island, around 1500 pairs. On some years a pair breeds on Inaccessible Island.

The Tristan albatross feeds on fish and cephalopods.