John Curtis Holmes (né Estes; August 8, 1944 – March 13, 1988), better known as John C. Holmes or Johnny Wadd (after the lead character he portrayed in a series of related films), was an American pornographic film actor. Holmes ranks among the most famous and prolific adult film performers, with documented credits for at least 573 films. Holmes was known for the exceptional size of his penis, which featured heavily in his marketing.

Near the end of his life, Holmes had been charged for his reputed involvement in the Wonderland murders of July 1981. He died from complications caused by AIDS in March 1988. Holmes was the subject of several books, a lengthy essay in Rolling Stone, two feature-length documentaries and was the inspiration for two Hollywood movies: Boogie Nights (1997) and Wonderland (2003).

John Holmes was born John Curtis Estes on August 8, 1944, in Ashville, Ohio, a small town located about 11 miles (18 km) south of Columbus. He was the youngest of four children born to 26-year-old Mary June (née Barton) Holmes, but the name of his father, railroad worker Carl Estes, was left blank on his birth certificate. Mary had married Edgar Harvey Holmes, who was the father of her three older children – Dale, Edward and Anne. She and Edgar were married and divorced three times, as is documented by wedding certificates dated April 13, 1936; August 13, 1945; and September 12, 1947. At the time of their first marriage in 1936, Edgar was 35 years old and divorced, while Mary was aged 17. After divorcing for the third and final time, Edgar and Mary each got married once more.

Holmes' mother was said to be a devout Southern Baptist and with her children regularly attended church in Millport, Ohio. By contrast, his stepfather Edgar was an alcoholic who would come home inebriated, stumble about the house and even vomit on the children. As a child, Holmes enjoyed a reprieve from his turbulent home life when he visited his maternal grandparents, John W. and Bessie (née Gillenwater) Barton.

On December 31, 1951, when Holmes was aged 7, his mother married Harold Bowman. Shortly afterward, Holmes and his family moved to the small town of Pataskala, Ohio, about seventeen miles east of Columbus. Holmes recalled that Bowman was a good father until his younger half-brother David was born, at which point Bowman reportedly lost interest in his stepchildren and began neglecting them.

In 1960, Holmes left home at age 15 and enlisted in the United States Army, with his mother's written permission. He spent most of the three years of his military service in West Germany in the Signal Corps. Upon his honorable discharge in 1963, Holmes moved to Los Angeles, California, where he worked in a variety of jobs, including selling goods door-to-door and tending the vats at a Coffee Nips factory. During his stint as an ambulance driver, Holmes met a nurse named Sharon Gebenini in December 1964. They married on August 21, 1965, in Fort Ord, California, after Holmes turned 21.

In April 1965, Holmes found work as a forklift operator at a meatpacking warehouse in Cudahy. However, repeated exposure to the freezing air in the large walk-in freezer after being outside inhaling the desert-hot air caused him severe health problems, leading to a collapsed lung on three occasions during the two years he worked there. Sharon also had health problems, as during the first seventeen months of her marriage to Holmes she miscarried three times.

John Holmes was to the adult film industry what Elvis Presley was to rock 'n' roll. He simply was The King.