Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Pacific. They are absent from the North Atlantic, although fossil remains show they once occurred there too and occasional vagrants turn up.

Albatrosses are amongst the largest of flying birds, and the great albatrosses (genus Diomedea) have the largest wingspans of any extant birds. The albatrosses are usually regarded as falling into four genera, but there is disagreement over the number of species.

Albatrosses are highly efficient in the air, using dynamic soaring and slope soaring to cover great distances with little exertion. They feed on squid, fish and krill by either scavenging, surface seizing or diving. Albatrosses are colonial, nesting for the most part on remote oceanic islands, often with several species nesting together. Pair bonds between males and females form over several years, with the use of 'ritualised dances', and will last for the life of the pair. A breeding season can take over a year from laying to fledging, with a single egg laid in each breeding attempt.

Of the 21 species of albatrosses recognised by the IUCN, 19 are threatened with extinction. Numbers of albatrosses have declined in the past due to harvesting for feathers, but today the albatrosses are threatened by introduced species such as rats and feral cats that attack eggs, chicks and nesting adults; by pollution; by a serious decline in fish stocks in many regions largely due to overfishing; and by long-line fishing. Long-line fisheries pose the greatest threat, as feeding birds are attracted to the bait, become hooked on the lines, and drown. Identified stakeholders such as governments, conservation organisations and people in the fishing industry are all working toward reducing this bycatch.

Taxonomy and evolution

The albatrosses comprise between 13 and 24 species (the number of species is still a matter of some debate, 21 being the most commonly accepted number) in 4 genera. The four genera are the great albatrosses (Diomedea), the mollymawks (Thalassarche), the North Pacific albatrosses (Phoebastria), and the sooty albatrosses or sooties (Phoebetria). Of the four genera, the North Pacific albatrosses are considered to be a sister taxon to the great albatrosses, while the sooty albatrosses are considered closer to the mollymawks.

The taxonomy of the albatross group has been a source of a great deal of debate. The Sibley-Ahlquist taxonomy places seabirds, birds of prey and many others in a greatly enlarged order Ciconiiformes, whereas the ornithological organisations in North America, Europe, South Africa, Australia and New Zealand retain the more traditional order Procellariiformes. The albatrosses can be separated from the other Procellariiformes both genetically and through morphological characteristics, size, their legs and the arrangement of their nasal tubes (see Morphology and flight).