irregular inlet of the Gulf of Alaska (Alaska, Gulf of), Alaska, U.S. It lies east of the Kenai Peninsula and spans about 90 to 100 miles (145 to 160 km). Hinchinbrook and Montague islands are at its oceanward entrance. The area lies within Chugach National Forest and has supported considerable fishing, mining, and forestry. Shipping is centred at the port of Valdez, the southern terminal for the Trans-Alaska Pipeline, and at Cordova. The sound was named by the British navigator Captain George Vancouver (Vancouver, George) in 1778 to honour the third son of King George III.

The area was devastated in 1964 by a massive earthquake, which unleashed a tsunami that affected coastal areas along the Gulf of Alaska, on the west coast of Canada and the United States, and in Hawaii; it also damaged or destroyed much of downtown Anchorage. Prince William Sound was also the site of a massive oil spill on March 24, 1989, when an Exxon Corporation tanker, the Exxon Valdez, ran aground on Bligh Reef. Delayed efforts to contain the spill and naturally strong winds and waves dispersed some 10.9 million gallons of North Slope crude oil across the sound. The spill eventually polluted thousands of miles of indented shoreline, as well as adjacent waters, as far south as the southern end of Shelikof Strait between Kodiak Island and the Alaska Peninsula. An intensive effort was subsequently mounted to clean up the oil spill and restore the sound's damaged ecosystem.