The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean. The river is 1,243 miles (2,000 km) long, and its largest tributary is the Snake River. Its drainage basin is roughly the size of France and extends into seven U.S. states and a Canadian province.

By volume, the Columbia is the fourth-largest river in the U.S., and it has the greatest flow of any North American river draining into the Pacific. The river's heavy flow and its relatively steep gradient give it tremendous potential for the generation of electricity. The 14 hydroelectric dams on the Columbia's main stem and many more on its tributaries produce more hydroelectric power than those of any other North American river.

The Columbia and its tributaries have been central to the region's culture and economy for thousands of years. They have been used for transportation since ancient times, linking the many cultural groups of the region. The river system hosts many species of anadromous fish, which migrate between freshwater habitats and the saline Pacific Ocean. These fish—especially the salmon species—provided the core subsistence for natives; in past centuries, traders from across western North America traveled to the Columbia to trade for fish.