Beckler River, Mountain brook in King County, United States.

Beckler River rises near Jack Pass in the central North Cascades and flows about 5 miles southeast to meet its main tributary, the Rapid River, then about 8 miles south into the South Fork Skykomish River. Its upper valley is narrow and steep, with forested slopes rising 4,000 feet above the floor; the valley widens slightly downstream and opens into the Skykomish valley in its last half-mile.

The Beckler River is named for Elbridge H. Beckler, chief engineer of the Great Northern Railway's Pacific extension from 1889 to 1893; nearby Beckler Peak also bears his name. In 1902 W. C. Guerin surveyed the area for a USGS mapping project, and prospectors had explored the region during the early 1890s, using the river as a route over Jack Pass to the North Fork Skykomish River.

The river's name honours Elbridge H. Beckler, chief engineer of the Great Northern Railway's Pacific extension from 1889 to 1893; nearby Beckler Peak also bears his name. In the early 1890s prospectors used the Beckler valley as an alternative route over Jack Pass to the North Fork Skykomish River, part of the rush to Monte Cristo.

Forest Service Road 65, the Beckler River Road, leaves U.S. Route 2 and runs north along the river to Jack Pass, where it meets Forest Service Road 63, the North Fork Skykomish Road. The Beckler River Campground sits on the banks of the lower river. The main river lies outside the Wild Sky Wilderness, though much of its drainage basin is inside it.

The water supports critical spawning grounds for Chinook and coho salmon within Mount Baker-Snoqualmie National Forest boundaries. Few visitors realize how important this small stream is to the region's salmon populations.