The McKenzie River is a 90-mile (145 km) tributary of the Willamette River in western Oregon in the United States. It drains part of the Cascade Range east of Eugene and flows westward into the southernmost end of the Willamette Valley. It is named for Donald McKenzie, a Scottish Canadian fur trader who explored parts of the Pacific Northwest for the Pacific Fur Company in the early 19th century. As of the 21st century, six large dams have been built on the McKenzie and its tributaries.