any member of more than a dozen species of long-winged oceanic birds belonging to the family Procellariidae (order Procellariiformes), which also includes the fulmars and the petrels. Typical shearwaters are the 12 to 17 species of the genus Puffinus, drab, slender-billed birds 35–65 centimetres (14–26 inches) in length. The common name shearwater describes the birds' habit of gliding on stiff wings along the troughs of waves. The name is sometimes also applied to the skimmers, an unrelated oceanic bird family (see skimmer).

Shearwaters nest in burrows on offshore islands and coastal hills in the North Atlantic, eastern South Atlantic, Mediterranean, and throughout most of the Pacific. Colonies may number hundreds of thousands of pairs, and at night, when the calling adults move in and out of the burrows, the din is deafening. A single egg is incubated in turn by the male and female, and the chick is raised by both parents.

Some of the most widespread Puffinus species are:

Sooty shearwater (P. griseus): length about 50 cm (19 ¹/₂ in.), wingspread about 85 cm (33 in.). Breeds near Australia, New Zealand, southern South America; winters in offshore waters of Atlantic and Pacific.

Common shearwater (P. puffinus): length 30–37 cm (11 ³/₄–14 ¹/₂ in.); several races given local names. Manx shearwater (P. p. puffinus) breeds in eastern North Atlantic; Newell's (P. p. newelli) in Hawaiian Islands; other races breed in the Mediterranean and in the waters around New Zealand.

Slender-billed or short-tailed shearwater (P. tenuirostris), called muttonbird in Australia and whalebird in Alaska; length 40 cm (15 ¹/₂ in.), breeds on islands in Bass Strait, Australia, and in Tasmania; remainder of year spent circumnavigating the Pacific; harvested in large numbers for meat and oil.