Point Marion Lock and Dam, previously known as Lock and Dam Number 8, is one of nine navigational structures on the Monongahela River between Pittsburgh, Pennsylvania and Fairmont, West Virginia. Maintained and built by the U.S. Army Corps of Engineers, the gated dam forms an upstream pool that is 11.2 miles (18.0 km) long, stretching to the base of the Morgantown Lock and Dam. It is located at river mile 90.5 (river kilometer 145.6).

There is one lock chamber on the left descending bank of the river at the dam, 84 feet (26 m) wide and 720 feet (220 m) long. The reservoir formed by the dam is also a municipal and industrial water supply.

List of crossings of the Monongahela River