Thomas Eugene Gaddis (September 14, 1908 – October 10, 1984) was an author from the United States, most noted for his book about convicted murderer Robert Stroud, who was known as the "Birdman of Alcatraz". Gaddis was born in Denver, Colorado. He wrote many non-fiction books, mostly biographies. In addition to Birdman of Alcatraz (1955), he wrote Killer: A Journal of Murder (1970) about serial killer Carl Panzram.
Gaddis wrote Birdman of Alcatraz in 1955. The biography became one of the nation's better-known prison biographies. Birdman of Alcatraz was the story of Robert Stroud, the grandson of a federal judge, who was sentenced to life imprisonment in solitary confinement after stabbing a guard to death in Leavenworth Federal prison in Kansas. Stroud was serving time in Leavenworth as a consequence of a slaying he committed in Alaska. While in solitary in Leavenworth, Stroud became an expert on birds, writing Stroud's Digest of the Diseases of Birds in Leavenworth from 1939 to 1941.
The 1962 film Birdman of Alcatraz starred Burt Lancaster as Stroud. Gaddis was portrayed by Edmond O'Brien.
Gaddis worked as a court consultant and on various writing projects. He is also well known for the following quote:
"Alcatraz, the federal prison with a name like the blare of a trombone, is a black molar in the jawbone of the nation's prison system."
He died in Portland, Oregon on October 10, 1984 at age 76.