Dragnet is an American media franchise created by actor and producer Jack Webb and owned by his company Mark VII Limited and Universal Pictures. It follows Los Angeles Police Department (LAPD) Detective Joe Friday and his partners as they conduct by-the-book police work and solve crimes in Los Angeles. Originating as a radio drama on NBC in 1949, Dragnet has been adapted into several successful television shows and films, though the franchise's popularity has reduced since Webb's death in 1982. Its name is derived from the police term "dragnet", a system of coordinated measures for apprehending criminals or suspects.

Dragnet is perhaps the most famous and influential police procedural crime drama in American media history. Webb's aims in Dragnet were for unpretentious acting and a realistic depiction of policing. The series portrayed police work as dangerous and heroic, and helped shape public perception of law enforcement in the 20th century, improving the public's opinion of police officers.

Dragnet remains a key influence on the police procedural genre. Its cultural impact is such that seven decades after its debut, elements of Dragnet are familiar to those who are otherwise unfamiliar with the franchise itself:

The opening of "The story you are about to hear is true" is derived from the fact that many works in the franchise are based on official LAPD case files. In some cases, the source material has been identified, including the following:

Dragnet began as a radio series, running on the NBC radio network from 1949 to 1957.

In 1951, Dragnet shifted to the field of television, running on NBC from 1951 to 1959. Most early episodes of the television series were dubbed or lip-synced adaptations of episodes of the radio show, but later episodes were original plotlines. Most of the cast members were veteran radio actors who could be relied upon to read the matter-of-fact dialogue naturally. A syndicated version of the series used the name Badge 714 to distinguish it from the network show. Friday's police badge number was 714.

Webb relaunched Dragnet in 1966, with NBC once again chosen to air the series. He tried to persuade Ben Alexander to rejoin him as Frank Smith. Alexander was then committed to an ABC police series, Felony Squad, and the producers would not release him. Webb reluctantly came up with a new character to take the role of Joe Friday's partner, calling upon his longtime friend Harry Morgan to play Officer Bill Gannon. Morgan had previously portrayed rooming-house proprietor Luther Gage in the 1949 radio series episode "James Vickers". George Fenneman returned as the show's primary announcer, with John Stephenson replacing Hal Gibney in the role of announcing the trial dates and subsequent punishments for the offenders. Fenneman replaced Stephenson in that role during the fourth season. Unlike the previous Dragnet series, the revival was produced and aired in color.

Webb produced a TV movie pilot for the new version of the show for Universal Television, although the pilot was not aired until January 1969. NBC bought the show on the strength of the movie, and it debuted as a midseason replacement for the sitcom The Hero on Thursday nights in January 1967. To distinguish it from the original, the year was included in the title of the show (i.e., Dragnet 1967). Although Friday had been promoted to lieutenant in the final episode of the 1950s production, Webb chose to have Friday revert to sergeant with his familiar badge, "714".