The passenger pigeon or wild pigeon (Ectopistes migratorius) is an extinct species of pigeon that was endemic to North America. Its common name is derived from the French word passager, meaning "passing by", due to the migratory habits of the species. The scientific name also refers to its migratory characteristics. The morphologically similar mourning dove (Zenaida macroura) was long thought to be its closest relative, and the two were at times confused, but genetic analysis has shown that the genus Patagioenas is more closely related to it than the Zenaida doves.
The passenger pigeon was sexually dimorphic in size and coloration. The male was in length, mainly gray on the upperparts, lighter on the underparts, with iridescent bronze feathers on the neck, and black spots on the wings. The female was , and was duller and browner than the male overall. The juvenile was similar to the female, but without iridescence. It mainly inhabited the deciduous forests of eastern North America and was also recorded elsewhere, but bred primarily around the Great Lakes. The pigeon migrated in enormous flocks, constantly searching for food, shelter, and breeding grounds, and was once the most abundant bird in North America, numbering around 3 billion, and possibly up to 5 billion. A very fast flyer, the passenger pigeon could reach a speed of . The bird fed mainly on mast, and also fruits and invertebrates. It practiced communal roosting and communal breeding, and its extreme gregariousness may be linked with searching for food and predator satiation.
Passenger pigeons were hunted by Native Americans, but hunting intensified after the arrival of Europeans, particularly in the 19th century. Pigeon meat was commercialized as cheap food, resulting in hunting on a massive scale for many decades. There were several other factors contributing to the decline and subsequent extinction of the species, including shrinking of the large breeding populations necessary for preservation of the species and widespread deforestation, which destroyed its habitat.