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The Sol Duc River (also spelled Soleduck) is a river in the U.S. state of Washington. About 78 miles (126 km) long, it flows west through the northwest part of the Olympic Peninsula, from the Olympic Mountains of Olympic National Park and Olympic National Forest, then through the broad Sol Duc Valley. Near the Pacific Ocean the Sol Duc River joins the Bogachiel River, forming the Quillayute River, which flows about 4 miles (6.4 km) to the Pacific Ocean at La Push. Although the Quillayute River is short, its large tributary rivers—the Sol Duc, Bogachiel, Calawah, and Dickey Rivers—drain the largest watershed of the northern Olympic Peninsula, 629 square miles (1,630 km²). The Sol Duc's watershed is the largest of the Quillayute's tributaries, at 219 square miles (570 km²).

The Sol Duc River's main tributaries are its two forks, the North Fork Sol Duc River and the South Fork Sol Duc River. Other notable tributaries include Bear Creek, Beaver Creek, and Lake Creek.

Much of the Sol Duc River's watershed is valuable timber land. Most of the forests have been logged at least once. The forests within Olympic National Park are protected.

U.S. Route 101 follows the Sol Duc River for many miles through Olympic National Forest and the Sol Duc Valley to the vicinity of Forks. The city of Forks is so named due to the close convergence of the Sol Duc, Bogachiel, and Calawah Rivers.