Elmer Wayne Henley Jr. (born May 9, 1956) is an American serial killer and accomplice to murder convicted in 1974 of the murder of six of the twenty-eight known victims of the Houston Mass Murders, which occurred in Houston and Pasadena, Texas, between 1970 and 1973.

One of two known accomplices to Dean Corll, Henley initially solely assisted Corll in the abduction of the victims before gradually and increasingly participating in their torture, murder and burial. He would shoot Corll to death on August 8, 1973, when he was seventeen years old before divulging his knowledge of and participation in the crimes to authorities.

Tried in San Antonio, Henley was convicted of six murders and sentenced to six consecutive terms of 99-years' imprisonment. He was not charged with the death of Corll, which prosecutors had previously ruled had been committed in self-defense. Henley did successfully appeal his conviction, although he was again convicted of six murders in June 1979. He is currently incarcerated within the Telford Unit in Bowie County, Texas.

At the time of the discovery of the crimes, the case was considered the worst example of serial murder in United States history.