John Wayne Gacy (March 17, 1942 – May 10, 1994) was an American serial killer who raped, tortured and murdered at least 33 teenage boys and young men between 1972 and 1978 in Cook County, Illinois (a part of metropolitan Chicago).

All of Gacy's known murders were committed inside his Norwood Park ranch house. His victims were typically induced to his address by force or deception, and all except one of his victims were murdered by either asphyxiation or strangulation with a makeshift garrote, as his first victim was stabbed to death. Gacy buried 26 of his victims in the crawl space of his home. Three other victims were buried elsewhere on his property, while the bodies of his last four known victims were discarded in the Des Plaines River.

Convicted of 33 murders, Gacy was sentenced to death on March 13, 1980 for 12 of those murders. He spent 14 years on death row before he was executed by lethal injection at Stateville Correctional Center on May 10, 1994.

Gacy became known as the "Killer Clown" because of his charitable services at fund-raising events, parades, and children's parties where he would dress as "Pogo the Clown"^[6] or "Patches the Clown", characters that he had created.