Don Walsh was an American oceanographer, U.S. Navy officer, and marine policy specialist. While aboard the bathyscaphe Trieste, he and Jacques Piccard made a record maximum descent in the Challenger Deep on January 23, 1960, to 35,813 feet (10,916 m). Later and more accurate measurements have measured it at 35,798 feet (10,911 m).

Trieste is a Swiss-designed, Italian-built deep-diving research bathyscaphe. In 1960, it became the first crewed vessel to reach the bottom of Challenger Deep in the Mariana Trench, the deepest point in Earth's seabed. The mission was the final goal for Project Nekton, a series of dives conducted by the United States Navy in the Pacific Ocean near Guam. The vessel was piloted by Swiss oceanographer Jacques Piccard and US Navy lieutenant Don Walsh. They reached a depth of about 10,916 metres (35,814 ft).