The thunderbird is a legendary creature in certain North American indigenous peoples' history and culture. It is considered a supernatural being of power and strength.
It is especially important, and frequently depicted, in the art, songs and oral histories of many Pacific Northwest Coast cultures, but is also found in various forms among some peoples of the American Southwest, East Coast of the United States, Great Lakes, and Great Plains. In modern times it has achieved notoriety as a purported cryptid, similar to creatures such as Bigfoot, and the Loch Ness Monster.
The thunderbird is said to create thunder by flapping its wings (Algonquian), and lightning by flashing its eyes (Algonquian, Iroquois).
The thunderbird myth and motif is prevalent among Algonquian peoples in the "Northeast", i.e., Eastern Canada (Ontario, Quebec, and eastward) and Northeastern United States, and the Iroquois peoples (surrounding the Great Lakes). The discussion of the "Northeast" region has included Algonquian-speaking people in the Lakes-bordering U.S. Midwest states (e.g., Ojibwe in Minnesota).
In Algonquian mythology, the thunderbird controls the upper world while the underworld is controlled by the underwater panther or Great Horned Serpent. The thunderbird creates not just thunder (with its wing-flapping), but lightning bolts, which it casts at the underworld creatures.
Thunderbirds in this tradition may be depicted as a spread-eagled bird (wings horizontal head in profile), but also quite commonly with the head facing forward, thus presenting an X-shaped appearance overall (see under §Iconography below).
The Ojibwe version of the myth states that the thunderbirds were created by Nanabozho for the purpose of fighting the underwater spirits. They were also used to punish humans who broke moral rules. The thunderbirds lived in the four directions and arrived with the other birds in the springtime. In the fall they migrated south after the ending of the underwater spirits' most dangerous season.
The Menominee of Northern Wisconsin tell of a great mountain that floats in the western sky on which dwell the thunderbirds. They control the rain and hail and delight in fighting and deeds of greatness. They are the enemies of the great horned snakes (the Misikinubik) and have prevented these from overrunning the earth and devouring mankind. They are messengers of the Great Sun himself.
The thunderbird motif is also seen in Siouan-speaking peoples, which include tribes traditionally occupying areas around the Great Lakes.
Ho-Chunk tradition states that a man who has a vision of a thunderbird during a solitary fast will become a war chief of the people.
Ethnographer George Amos Dorsey transcribed a tale from the Arikaras with the title The Boy who befriended the Thunderbirds and the Serpent: a boy named Antelope-Carrier finds a nest with four young thunderbirds; their mother comes and tells the human boy that a two-headed Serpent comes out of the lake to eat the young.
In Algonquian images, an X-shaped thunderbird is often used to depict the thunderbird with its wings alongside its body and the head facing forwards instead of in profile.
The depiction may be stylized and simplified. A headless X-shaped thunderbird was found on an Ojibwe midewiwin disc dating to 1250–1400 CE. In an 18th century manuscript (a "daybook" ledger) written by the namesake grandson of Governor Matthew Mayhew, the thunderbird pictograms varies from "recognizable birds to simply an incised X".
American science historian and folklorist Adrienne Mayor and British historian Tom Holland have both suggested that indigenous thunderbird stories are based on discoveries of pterosaur fossils by Native Americans. However, it has also been noted that,[by whom?] despite variations, the common design elements of the motif within different tribal groups across the continent appear distinct from the makeup of the suggested prehistoric flying reptile, such as eagle or raptor-like avian feathered wings and tail, along with a vastly different head shape, perhaps with the exception of some Pacific Northwest imagery.