The Rapid River is a tributary of the Beckler River in the U.S. state of Washington in the United States. It is 13 miles (21 km) long, with a drainage basin of 41 square miles (106 km2).
The Rapid River originates at 47°49′19″N 121°7′28″W / 47.82194°N 121.12444°W, at Grouse Lake and at 47°49′40″N 121°04′24″W / 47.82778°N 121.07333°W on the west slopes of Jove Peak on the crest of the Cascades, six and nine miles east of the Beckler River. The latter source flows through Lake Janus (at 4,146 ft) before meeting the Grouse Lake source creek, whereafter the river continues southwest. An early tributary comes from 4,742 ft high Dow Lake, southwest of Union Pass and Union Peak, also on the Cascade crest. The Pacific Crest Trail follows the crest and parts of the high Rapid River basin. Both Jove and Union peaks are on the high crest of the Cascade Range, separating the Rapid River's drainage basin from the Little Wenatchee River drainage to the east. While the waters of the Rapid River ultimately empty into Puget Sound those of the Little Wenatchee enter the Columbia River via the Wenatchee River.