The original British version debuted on 4 September 1998, and was aired until its final episode on 11 February 2014; a revived series of seven episodes to commemorate its 20th anniversary in 2018, were aired from 5 to 11 May. Since its debut, international variants of the game show have been aired in around 160 countries worldwide.
The format of the show was created by David Briggs, Mike Whitehill and Steven Knight, who had earlier created a number of the promotional games for Tarrant's morning show on Capital FM radio, such as the bong game. Tentatively known as Cash Mountain, the show took its finalised title from a song written by Cole Porter for the 1956 film High Society, starring by Frank Sinatra and Celeste Holm. Since the original version launched, several individuals have claimed that they originated the format and that Celador had breached their copyright and took the production company to court, but each claim was later settled out-of-court on an agreement/settlement..
In March 2006, original producer Celador announced that it was seeking to sell the worldwide rights to Millionaire, together with the rest of its British programme library, as the first phase of a sell-off of the company's format and production divisions. The idea to transform the UK programme into a global franchise was conceived by British television producer Paul Smith. He laid out a series of rules that the international variants in the franchise were to follow: for example, all hosts were required to appear on-screen wearing Armani suits, as Tarrant did in the UK; producers were forbidden from hiring local composers to create original music, instead using the same music cues used by the British version; and the lighting system and set design were required to adhere faithfully to the way they were presented on the British version. However, some of Smith's rules have been slightly relaxed over the years as the franchise's history has progressed.
Millionaire and all of Celador's other programmes were ultimately acquired by Dutch company 2waytraffic. Two years later, Sony Pictures Entertainment purchased 2waytraffic for £137.5 million. The format of the show is currently owned and licensed by Sony Pictures Television; however, the U.S. version is distributed not by Sony but by the Walt Disney Company's in-home sales and content distribution firm, Disney–ABC Domestic Television.
A group of contestants on each episode play a preliminary round called "Fastest Finger First". All are given a question by the host and four answers which must be placed within a particular order; in the original version and pre-2003 episodes of the Australian version, contestants have to simply answer a multiple-choice question. If any contestants are visually impaired, the host reads the question and four choices all at once, then repeats the choices after the music for this round begins. The contestant who not only answers correctly, but in the fastest time, goes on to play the main game. In the event that no one gets the question right, another question is given; if two or more contestants answer correctly but with the same time, they are given a tie-breaker amongst them to determine who will move on. This round is only used when a new contestant is being chosen to play the main round, and can be played more than once in an episode amongst those remaining within the group seeking to play the main game. In celebrity editions, the round is not used; celebrities automatically take part in the main game.