William "Bill" Homer Genaust (October 12, 1906 – March 4, 1945) was a United States Marine Corps sergeant who was missing in action during the battle of Iwo Jima while serving as a war photographer in World War II. He is best known for filming the second U.S. flag-raising on top of Mount Suribachi on February 23, 1945. Genaust operated a then-modern and lightweight 16 millimeter motion picture camera which used 50-foot color film cassettes. His motion picture of the flag-raising became one of the best-known film clips of the war, and documents the event famously depicted in the Marine Corps War Memorial in Arlington, Virginia. Genaust was reportedly killed in action nine days later, shot and killed by Japanese soldiers hiding in a cave. Because bulldozers sealed the cave his body was not recovered.