The trumpeter swan is a species of swan found in North America. The heaviest living bird native to North America, it is also the largest extant species of waterfowl, with a wingspan of 185 to 304.8 cm. It is the American counterpart and a close relative of the whooper swan of Eurasia, and even has been considered the same species by some authorities. By 1933, fewer than 70 wild trumpeters were known to exist, and extinction seemed imminent, until aerial surveys discovered a Pacific population of several thousand trumpeters around Alaska's Copper River. Careful reintroductions by wildlife agencies and the Trumpeter Swan Society gradually restored the North American wild population to over 46,000 birds by 2010.

Swans are birds of the genus Cygnus within the family Anatidae. The swans' closest relatives include the geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae.