The Miller River is a river in King County, Washington. Named for 1890s prospector John Miller, it is a tributary of the Skykomish River, which it joins near the community of Miller River (which was, prior to World War I, known as Berlin). The Miller River is about 3.5 miles (5.6 km) long from the confluence of its main tributaries, the East Fork and West Fork. Miller River Campground is located just downriver from the confluence.