The American Ornithological Society was created in 2016 as a merger between the American Ornithologists' Union (AOU), founded in 1883 and the oldest organization in the New World devoted to the scientific study of birds, and the Cooper Ornithological Society (COS), founded in 1893.

The mission of the AOS is to advance the scientific understanding of birds and disseminate ornithological knowledge, to enrich ornithology as a profession and mentor young professionals, and to promote a rigorous scientific basis for the conservation of birds.

The AOS publishes two of the foremost ornithological journals in the world: The Auk: Ornithological Advances and The Condor: Ornithological Applications; the Checklist of North and Middle American Birds and the complementary Checklist of South American Birds; the award-winning Series in Avian Biology book series and the Ornithological Monograph series; and co-sponsors Birds of North America (published online through the Cornell Lab of Ornithology).