The Gros Ventre, also known as the Aaniiih, A'aninin, Haaninin, Atsina, and White Clay, are a historically Algonquian-speaking Native American tribe located in northcentral Montana. Today, the Gros Ventre people are enrolled in the Fort Belknap Indian Community of the Fort Belknap Reservation of Montana, a federally recognized tribe with 7,000 members, also including the Assiniboine people.

Montana is a landlocked state in the Mountain West subregion of the Western United States. It borders Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, and the Canadian provinces of Alberta, British Columbia, and Saskatchewan to the north. It is the fourth-largest state by area, the eighth-least populous state, and the third-least densely populated state. Its capital is Helena, while the most populous city is Billings. The western half of the state contains numerous mountain ranges, while the eastern half is characterized by western prairie terrain and badlands, with smaller mountain ranges found throughout the state.