The Mendocino War was a conflict between the Yuki (mainly Yuki tribes) and white settlers in Mendocino County, California between July 1859 and January 18, 1860. It was caused by settler intrusion and slave raids on native lands and subsequent native retaliation, resulting in the deaths of hundreds of Yuki.

In 1859, a band of locally sponsored rangers led by Walter S. Jarboe, called the Eel River Rangers, raided the countryside in an effort to remove the natives from settler territory and move them onto the Nome Cult Farm, an area near the Mendocino Indian Reservation. By the time the Eel River Rangers were disbanded in 1860, Jarboe and his men had killed 283 warriors, captured 292, killed countless women and children, and only suffered 5 casualties themselves in just 23 engagements. The bill to the state for the rangers' services amounted to $11,143.43. Scholars, however, state that the damage to the area and natives in particular was even higher than reported, especially given the vast number of raiding parties formed outside of the Eel River Rangers.

Other settlers formed their own raiding parties against the natives, joining Jarboe in his mission to rid Round Valley of its native population. Those that survived were moved to the Nome Cult Farm, where they experienced hardships typical of the reservation system of the day. After the conflict, contemporaries claimed that the conflict was more of a slaughter than a war, and later historians have labeled it a genocide.