The Cayuse War is an armed conflict that takes place in the Northwestern United States from 1847 to 1855 between the Cayuse people of the region and the United States Government and local American settlers.

Caused in part by the influx of disease and settlers to the region, the immediate start of the conflict occurs in 1847 when the Whitman Massacre takes place at the Whitman Mission near present day Walla Walla, Washington when fourteen people are killed in and around the mission.

Over the next few years the Provisional Government of Oregon and later the United States Army battles the Indians east of the Cascades.

This is the first of several wars between the natives and American settlers in that region that would lead to the negotiations between the United States and natives tribes of the Columbia Plateau, creating a number of Indian reservations.