Thunderbirds is a British science fiction television series created by Gerry and Sylvia Anderson, filmed by their production company AP Films (APF) and distributed by ITC Entertainment. It was filmed between 1964 and 1966 using a form of electronic marionette puppetry called "Supermarionation" combined with scale model special effects sequences. Two series, totalling 32 fifty-minute episodes, were made; production ended with the sixth episode of the second series after Lew Grade, APF's financial backer, failed in his efforts to sell the programme to US network television.

Set in the 2060s, Thunderbirds was a follow-up to the earlier Supermarionation productions Four Feather Falls, Supercar, Fireball XL5 and Stingray. It concerns the exploits of International Rescue,

a life-saving organisation with a secret base on an island in the Pacific Ocean. International Rescue operates a fleet of technologically-advanced rescue vehicles, headed by five craft called the Thunderbird machines. The main characters are the leader of International Rescue, ex-astronaut Jeff Tracy, and his five adult sons, who pilot the Thunderbirds.

Thunderbirds premiered in September 1965 on the ITV network and has since aired in at least 66 countries. Besides tie-in merchandise, it was followed by two feature films: Thunderbirds Are Go and Thunderbird 6. Periodically repeated, it was adapted for radio in the 1990s and has influenced many TV programmes and other media. Its other adaptations include an anime reimagining (Thunderbirds 2086), a live-action film (Thunderbirds) and a part-CGI, part-live-action remake (Thunderbirds Are Go). Three supplementary episodes, based on tie-in audio plays and made using the same puppet techniques as the original, have also been produced.

Widely regarded as the Andersons' most popular and commercially successful series, Thunderbirds has been praised for its special effects, directed by Derek Meddings, and its musical score by Barry Gray. It is also remembered for its title sequence, which begins with an oft-quoted countdown by Jeff Tracy voice actor Peter Dyneley: "5, 4, 3, 2, 1 – Thunderbirds Are Go!" A real-life search and rescue service, the International Rescue Corps, was named after the organisation featured in the series.