Happy Days is an American sitcom television series that aired first-run on the ABC network from January 15, 1974, to September 24, 1984, with a total of 255 half-hour episodes spanning eleven seasons. Created by Garry Marshall, the series was one of the most successful of the 1970's, an idealized vision of life in the mid-1950's to mid-1960's Midwestern United States, and starred Ron Howard as young Richie Cunningham, Henry Winkler as his friend, Arthur "Fonzie" Fonzarelli, and Tom Bosley and Marion Ross as Richie's parents, Howard and Marion Cunningham. Although it opened to mixed reviews from critics, Happy Days became successful and popular over time.

The series began as an unsold pilot starring Howard, Ross and Anson Williams, which aired in 1972 as a segment entitled Love and the Television Set (later retitled Love and the Happy Days for syndication) on ABC's anthology show, Love, American Style. Based on the pilot, director George Lucas cast Howard as the lead in his 1973 film, American Graffiti, causing ABC to take a renewed interest in the pilot. The first two seasons of Happy Days focused on the experiences and dilemmas of "innocent teenager" Richie Cunningham, his family, and his high school friends, attempting to "honestly depict a wistful look back at adolescence". Initially a moderate success, the series' ratings began to fall during its second season, causing Marshall to retool it emphasizing broad comedy and spotlighting the previously minor character of Fonzie, a "cool" biker and high school dropout. Following these changes, Happy Days became the number-one program in television in 1976–1977, Fonzie became one of the most merchandised characters of the 1970's, and Henry Winkler became a major star. The series also spawned a number of spin-offs, including Laverne and Shirley and Mork and Mindy.