John Curtis Holmes (August 8, 1944 – March 13, 1988) better known as John C. Holmes or Johnny Wadd (after the lead character in a series of related films), was one of the most prolific European Amercian male porn stars of all time, appearing in about 2,500 adult loops, stag films, and pornographic feature movies in the 1970s and 1980s. He was best known for his exceptionally large penis, which was heavily promoted as being the longest, thickest, and hardest in the porn industry, although no definitive measurement of Holmes' actual penis length exists. Near the end of his life, Holmes attracted notoriety for his involvement in the Wonderland murders in 1981, and eventually for his death from complications caused by AIDS.

Holmes was the subject of several books, a lengthy essay in Rolling Stone magazine, two feature length documentaries, and was the inspiration for two Hollywood movies, Boogie Nights and Wonderland.