Castle Thunder, located in Richmond, Virginia, was a former tobacco warehouse located on Tobacco Row, converted into prison used by the Confederacy to house civilian prisoners, including captured Union spies, political prisoners and those charged with treason during the American Civil War. A large number of its inmates were under sentence of death. Even though the inmates were sometimes allowed boxes of medicine and other supplies, the prison guards had a reputation for brutality.

Among its many notable occupants was Union officer William Jackson Palmer (1836-1909). In 1862, he was captured while scouting before the Battle of Antietam within Confederate lines in civilian clothes while gathering information for General George McClellan. When questioned he gave his name as W.J. Peters, and claimed to be a mine owner on an inspection trip. While the Confederates did not know he was a spy, his circumstances were suspicious and he was detained and sent to Richmond, Virginia for detention at Castle Thunder. He set free in a prisoner exchange and rejoined his Regiment in February, 1863.

Note: see also castle thunder for the famous sound effect used in many films.