Jacob Beser (May 15, 1921 – June 16, 1992) was a lieutenant in the United States Army Air Forces who served during World War II. Beser was the radar specialist aboard the Enola Gay on August 6, 1945, when it dropped the Little Boy atomic bomb on Hiroshima. Three days later, Beser was a crewmember aboard Bockscar when "Fat Man" was dropped on Nagasaki. He was the only person to have served as a strike crew member of both of the 1945 atomic bomb missions.