Glen Canyon Dam is a concrete arch dam on the Colorado River in northern Arizona in the United States, near the town of Page. The dam was built to provide hydroelectricity and flow regulation from the upper Colorado River Basin to the lower. Its reservoir is called Lake Powell, and is the second largest artificial lake in the country, extending upriver well into Utah. The dam is named for Glen Canyon, a colorful series of gorges, most of which now lies under the reservoir.

The dam was proposed in the 1950s as part of the Colorado River Storage Project, a U.S. Bureau of Reclamation (USBR) federal water project that would develop reservoir storage on the upper Colorado River and several of its major tributaries. The project's main purpose was to provide water storage to ensure the delivery of sufficient water to the lower basin during years of drought, so as to allow the upper basin to better utilize its allocation of river flow as designated in the 1922 Colorado River Compact. However, problems arose when the USBR proposed to build dams in the federally protected Echo Park canyon in Utah. After extensive policy disputes and legal challenges with environmental organizations such as the Sierra Club, they settled for a high dam at Glen Canyon.

Construction of Glen Canyon Dam started in 1956 and was not finished until 1966. When the reservoir filled, the dam began to deliver a regulated flow of water downstream and a supply of electricity to the region. In 1983, major floods nearly led to the dam's collapse, but disaster was averted by a close margin. By suppressing floods and other factors that once characterized the Colorado, the dam has led to major physical and ecological changes in the lower river. Controversy continues over the effects both positive and negative of the dam, which has also been criticized in many literary works.