The Round Valley War was an 1887 conflict between American Colonists and Yuki Indians on the Round Valley Indian Tribes of the Round Valley Reservation in California. The conflict started as colonists were beginning to encroach on reservation lands, making the already difficult circumstances for the Yuki people who had been placed there following the Mendocino War even more unfavourable. The Federal Office of Indian Affairs moved to have the trespassing settlers evicted. The settlers turned to local authorities and the Sheriff of Mendocino arrested the federal officer who had filed the accusations against the settlers.