Glines Canyon Dam, Historic dam site in Olympic National Park, United States.

Glines Canyon Dam was a 210-foot (64 m) concrete arch dam on the Elwha River in Clallam County, Washington, built in 1927. It impounded Lake Mills reservoir and stood 13 miles (21 km) upriver from the river mouth, within Olympic National Park. The dam was demolished in 2014, making it the tallest dam ever intentionally breached.

The dam was built as a concrete arch structure in the 1920s to supply power to the growing region. After 87 years of operation, it was completely removed, allowing the Elwha to flow freely once again.

The dam's name comes from Glines Canyon on the Elwha, and its powerhouse, dam and water-conveying system form a 7-acre historic district listed on the National Register of Historic Places in 1988. Visitors today reach the Glines Canyon Spillway Overlook, a viewpoint over the former dam site, where the drained Lake Mills basin is being revegetated.

The Glines Canyon Spillway Overlook is reached from the Olympic Hot Springs Road side of the Elwha valley, where a short trail leads to a viewpoint over the former dam site. The road is closed to vehicles beyond the Madison Falls area, so access is on foot or by bicycle. Check road and trail conditions before setting out.

The dam was systematically dismantled between 2011 and 2014 in one of the largest deconstruction projects worldwide. The effort restored one of the longest salmon migration routes in the country.