North American Plains Indian people of Siouan stock living mainly on Fort Berthold Reservation in North Dakota, U.S. They speak a Siouan language.
They were mistakenly identified as a group known to French trappers as Gros Ventres , and sometimes they are called Gros Ventres of the Missouri. Originally the Hidatsa (whose name means "People of the Willow") lived on the upper Missouri River in semipermanent villages. They raised corn, beans, and squash and hunted bison. Hidatsa social organization included age-graded military societies; there were also various clans based on maternal descent. The sun dance was the major religious ceremony. Together with the Mandan , with whom they had peaceful relations for more than 200 years, they exchanged traditional goods with European traders for guns, knives, and other items. In the mid-1800s disease and war with the Dakota ( Sioux ) sharply reduced their number. Only some 625 people claimed sole Hidatsa descent in the 2000 U.S. census. Together the Mandan, the Arikara, and the Hidatsa form the Three Affiliated Tribes.