The Cayuse are a Native American tribe in what is now the state of Oregon in the United States. The Cayuse tribe shares a reservation and government in northeastern Oregon with the Umatilla and the Walla Walla tribes as part of the Confederated Tribes of the Umatilla Indian Reservation. The reservation is located near Pendleton, Oregon, at the base of the Blue Mountains.

The Umatilla Indian Reservation is an Indian reservation in the Pacific Northwest of the United States. It was created by The Treaty of 9 June 1855 between the United States and members of the Walla, Cayuse, and Umatilla tribes. It lies in northeastern Oregon, east of Pendleton. The reservation is mostly in Umatilla County, with a very small part extending south into Union County. It is managed by the three Confederated Tribes of the Umatilla Indian Reservation.