Harry Glicken (1958–June 3, 1991) was an American volcanologist. He was killed on June 3, 1991 by a pyroclastic flow on Mount Unzen in Japan in an eruption that killed 42 other people, including volcanologists Katia and Maurice Krafft. Glicken notably worked at Mount St. Helens in the United States before and after its famous 1980 eruption, and he felt responsible for the death of fellow volcanologist David A. Johnston, who switched with Glicken so that the latter could attend an interview.