Ronald DeFeo Jr. killed six members of his family in Amityville, New York, events that later inspired the book The Amityville Horror and a subsequent media franchise.

Ronald Joseph DeFeo Jr. was an American mass murderer who was tried and convicted for the 1974 killings of his father, mother, two brothers, and two sisters in Amityville, New York. He was found guilty of six counts of second degree murder and was sentenced to 25 years to life. DeFeo died in March 2021. The case inspired the book and film versions of The Amityville Horror.

Amityville is a village in the Town of Babylon in Suffolk County, on the South Shore of Long Island, in New York, United States. The population was 9,500 at the 2020 census. The village maintains its own accredited law enforcement agency, the Amityville Police Department.

The Amityville Horror is a book by American author Jay Anson, published in September 1977. It is also the basis of a series of films released from 1979 onward. The book is based on the claims of paranormal experiences by the Lutz family but has led to controversy and lawsuits over its truthfulness.

The Amityville haunting is a modern folk story based on the true crimes of Ronald DeFeo Jr. On November 13, 1974, DeFeo shot and killed six members of his family at 112 Ocean Avenue, Amityville, on the south shore of Long Island. He was convicted of second-degree murder in November 1975. In December 1975, George and Kathy Lutz and their three children moved into the house. After 28 days, the Lutzes left the house, claiming to have been terrorized by paranormal phenomena while living there. The house became the subject of numerous investigations by journalists, skeptics, and paranormal researchers, including Ed and Lorraine Warren. These events served as the historical basis for Jay Anson's 1977 novel The Amityville Horror, which was followed by a number of sequels and was adapted into a film of the same name in 1979. Since then, many films have been produced that draw explicitly, to a greater or lesser extent, from these historical and literary sources. As Amityville is a real town and the stories of DeFeo and the Lutzes are historical, there can be no proprietary relationship to the underlying story elements associated with the Amityville haunting. As a result of this, there has been no restriction on the exploitation of the story by film producers, which is the reason that most of these films share no continuity, were produced by different companies, and tell widely varying stories.