The Blackfoot Confederacy, Niitsítapi, or Siksikáí'tsitapi (ᖹᒧᐧᒣᑯ, meaning "the people" or "Blackfoot-speaking real people"), is a historic collective name for linguistically related groups that make up the Blackfoot or Blackfeet people: the Siksika ("Blackfoot"), the Kainai ("Many Chiefs") or Blood, and two sections of the Peigan or Piegan or Piikani ("Splotchy Robe") – the Northern Piikani (Aapátohsipikáni) and the Southern Piikani (Amskapi Piikani or Pikuni). Broader definitions include groups such as the Tsúùtínà (Sarcee) and A'aninin (Gros Ventre) who spoke quite different languages but allied with or joined the Blackfoot Confederacy.
Historically, the member peoples of the Confederacy were nomadic bison hunters and trout fishermen, who ranged across large areas of the northern Great Plains of western North America, specifically the semi-arid shortgrass prairie ecological region. They followed the bison herds as they migrated between what are now the United States and Canada, as far north as the Bow River. In the first half of the 18th century, they acquired horses and firearms from white traders and their Cree and Assiniboine go-betweens. The Blackfoot used these to expand their territory at the expense of neighboring tribes.