Rocky Boy's Indian Reservation (also known as Rocky Boy Reservation) is one of seven Native American reservations in the U.S. state of Montana. Established by an act of Congress on September 7, 1916, it was named after Ahsiniiwin (Stone Child, incorrectly originally translated as Rocky Boy), the chief of the Chippewa band, who had died a few months earlier. It was established for landless Chippewa (Ojibwe) Indians in the American West, but within a short period of time many Cree (nēhiyaw) and Métis were also settled there. Today the Cree outnumber the Chippewa on the reservation. The Bureau of Indian Affairs (BIA) recognizes it (and the tribe) as the Chippewa Cree Reservation.

The reservation is located in Hill and Chouteau counties in north central Montana, about 40 miles (64 km) from the Canada–U.S. border. It has a total land area of 171.4 square miles (444 km²), which includes extensive off-reservation trust lands. The reservation reportedly has 3,323 enrolled members, 55% of the total 6,177 enrolled members in the tribe.

The reservation was established by congressional statute on September 7, 1916 (39 Stat. 739, Sec. 10), to provide land for the Rocky Boy's Band of Chippewa Indians, who had been forced out of territory in Minnesota and were landless. The Rocky Boy's Indian Reservation is in the Bears Paw Mountains in north-central Montana. According to the map of Montana, the reservation takes in land within the boundaries of Hill and Chouteau counties, about 40 miles (64 km) south of the Canada–United States border. It is the smallest reservation in the state in terms of land area, with a total land area of 171.4 square miles (443.9 km²), which includes extensive off-reservation trust lands. The population was 3,323 at the 2010 census, an increase of 24 percent compared to 2000. Three other reservations of the seven in the state also had population growth during this period.

The Bureau of Indian Affairs' Labor Force Report of 2005 reported 5,656 enrolled members in the tribe. The largest community of the reservation is Box Elder, although a small part of Box Elder extends off reservation lands. More than 80% of the tribal enrolled members are classifiable as "adoptees" under the tribal constitution, as they have non-Chippewa tribal origin.

Rocky Boy's unusual name was derived from the English mistranslation of the name of the tribal chief, Ahsiniiwin (in the Chippewa/Anishanaabe language). His name was closer in meaning to "Stone Child". The Chippewa who are descendants of Chief Rocky Boy say his name is Asiniweyin, meaning "Stone Being", or "Being of Stone".

The Department of Interior refers to the Chippewa-Cree Tribe as being the recognized tribe on the reservation, but this is a term of convenience. The Chippewa and Cree peoples are distinct tribes among the several that are part of the larger Anishinaabe family.

Chief Rocky Boy wrote to the Bureau of Indian Affairs and later to President Theodore Roosevelt on January 14, 1902, asking the U.S. government for land, housing, and education for his band of Chippewa Indians, composed of 130 men, women and children. They had been forced out of areas to the east and were landless. Also among landless Indians in Montana were a band of Cree.

Chief Rocky Boy (Ahsiniiwin) worked with Republican Senator Joseph M. Dixon, writer Frank Bird Linderman, and other influential individuals in Montana, including painter Charles Russell, to achieve his goal. He lived mainly in north central Montana, although he also traveled to southwestern and western areas of the state. The Rocky Boy Band was listed at 75 in a 1908 census that was certified by the Department of the Interior. Another 39 were listed separately as affiliated persons but not Chippewa, by agent Thralls B. Wheat, who was responsible for land allotments. ^{[citation needed]}