The Avengers is a British espionage television series that aired from 7 January 1961 to 21 April 1969. It initially focused on David Keel (Ian Hendry), aided by John Steed (Patrick Macnee). Ian Hendry left after the first series; Steed then became the main character, partnered with a succession of assistants. His most famous assistants were intelligent, stylish, and assertive women: Cathy Gale (Honor Blackman), Emma Peel (Diana Rigg), and Tara King (Linda Thorson). Dresses and suits for the series were made by Pierre Cardin.

The series screened as one-hour episodes for its entire run. The first episode, "Hot Snow", aired on 7 January 1961. The final episode, "Bizarre", aired on 21 April 1969 in the United States, and on 17 May 1969 in the United Kingdom.

The Avengers was produced by ABC Weekend TV, a contractor within the ITV network. After a merger with Rediffusion London in July 1968, ABC Weekend became Thames Television, which continued production of the series, subcontracted to ABC Television Films. By 1969, The Avengers was shown in more than 90 countries. ITV produced a sequel series, The New Avengers (1976–1977), with Patrick Macnee returning as John Steed, and two new partners. In 2004 and 2007, The Avengers was ranked No. 17 and No. 20 on TV Guide's Top Cult Shows Ever.