Bennett County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 3,381. Its county seat is Martin. The county lies completely within the exterior boundary of the Pine Ridge Indian Reservation. To the east is the Rosebud Indian Reservation, occupied by Sicangu Oyate, also known the Upper Brulé Sioux Nation and the Rosebud Sioux Tribe (RST), a branch of the Lakota people.

The Pine Ridge Indian Reservation, also called Pine Ridge Agency, is an Oglala Lakota Indian reservation located in the U.S. state of South Dakota, with a small portion of it extending into Nebraska. Originally included within the territory of the Great Sioux Reservation, Pine Ridge was created by the Act of March 2, 1889, 25 Stat. 888. in the southwest corner of South Dakota on the Nebraska border. It consists of 3,468.85 sq mi (8,984 km2) of land area and is one of the largest reservations in the United States.