Marcus Whitman (September 4, 1802 – November 29, 1847) is an American physician and missionary in the Oregon Country.

Along with his wife Narcissa Whitman, he starts a mission to the Cayuse in what is now southeastern Washington state in 1836.

The area later develops as a trading post and stop along the Oregon Trail, and the city of Walla Walla, Washington develops near there.

In 1843, Whitman leads the first large party of wagon trains along the Oregon Trail to the West, establishing it as a viable route for the hundreds of thousands of emigrants who use the trail in the following decade.

Settlers encroach on the Cayuse near the Whitman mission.

Following the deaths of all the Cayuse children and half their adults from a measles epidemic in 1847, in which the Cayuse suspect the Whitmans' responsibility, they kill the Whitmans and twelve other settlers in what becomes known as the Whitman Massacre.

Continuing warfare by settlers reduced the Cayuse numbers further and they eventually join the Nez Perce tribe to survive.