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 made between 1964 and 1966 using a form of electronic marionette puppetry (dubbed "Supermarionation") combined with scale model special effects sequences. Two series, totalling thirty-two 50-minute episodes, were filmed; production ended with the completion of the sixth episode of the second series after Lew Grade, the Andersons' financial backer, failed in his bid to sell the programme to American network television.

Set in the 2060s, Thunderbirds is a follow-up to the earlier Supermarionation productions Four Feather Falls, Supercar, Fireball XL5 and Stingray. It follows the exploits of International Rescue, a life-saving organisation equipped with technologically advanced land, sea, air and space rescue craft; these are headed by a fleet of five vehicles named the Thunderbirds and launched from the organisation's secret base of operations in the Pacific Ocean. The main characters are ex-astronaut Jeff Tracy, leader of International Rescue, and his five adult sons, who pilot the Thunderbird machines.

Thunderbirds debuted in September 1965 on the ITV network. The series was exported to around 30 countries during the 1960s. Periodically repeated, it was adapted for radio in the 1990s and has influenced many TV programmes and other media. Besides tie-in merchandise, the series has been followed by two feature film sequels – Thunderbirds Are Go and Thunderbird 6 – as well as an anime adaptation, a mime theatre show and a live-action film. A remake series premiered in 2015; the same year, three new episodes, based on tie-in audio plays and made using the same techniques as the original series, were created to mark its 50th anniversary.

Widely regarded as the Andersons' most popular and commercially successful series, Thunderbirds has been praised for its special effects (directed by Derek Meddings) and musical score (composed 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!"