The film adheres closely to the novel, but also injects a fair amount of humor. It was shot by David Watkin, with an eye for period detail. The fight scenes were choreographed by master swordsman William Hobbs.
Having learned swordsmanship from his father, the young country bumpkin d'Artagnan arrives in Paris with dreams of becoming a king's musketeer. Unaccustomed to the city life, he makes a number of clumsy faux pas. First he finds himself insulted, knocked out and robbed by the Comte de Rochefort, an agent of Cardinal Richelieu, and once in Paris comes into conflict with three musketeers, Athos, Porthos, and Aramis, each of whom challenges him to a duel for some accidental insult or embarrassment. As the first of these duels is about to begin, Jussac arrives with five additional swordsmen of Cardinal Richelieu's guards. D'Artagnan sides with the musketeers in the ensuing street fight and becomes their ally in opposition to the Cardinal, who wishes to increase his already considerable power over the king, Louis XIII. D'Artagnan also begins an affair with his landlord's wife, Constance Bonacieux, who is dressmaker to the Queen, Anne of Austria.
Meanwhile, the Duke of Buckingham, former lover of the Queen, turns up and asks for something in remembrance of her; she gives him a necklace with twelve settings of diamonds, a gift from her husband. From the Queen's treacherous lady in waiting, the Cardinal learns of the rendezvous and suggests to the none-too-bright King to throw a ball in his wife's honor, and request she wear the diamonds he gave her. The Cardinal also sends his agent Milady de Winter to England, who seduces the Duke and steals two of the necklace's diamonds.
Meanwhile, the Queen has confided her troubles in Constance, who asks d'Artagnan to ride to England and get back the diamonds. D'Artagnan and the three musketeers set out, but on the way the Cardinal's men attack them. Only d'Artagnan and his servant make it through to Buckingham, where they discover the loss of two of the diamond settings. The Duke replaces the two settings, and d'Artagnan races back to Paris. Porthos, Athos, and Aramis, wounded but not dead as d'Artagnan had feared, aid the delivery of the complete necklace to the Queen, saving the royal couple from the embarrassment which the Cardinal had plotted.
Captain Tréville eventually inducts d'Artagnan into the Musketeers of the King's Guard.Michael York as d'Artagnan
Oliver Reed as Athos
Frank Finlay as Porthos / O'Reilly
Richard Chamberlain as Aramis
Jean-Pierre Cassel as King Louis XIII of France
Geraldine Chaplin as Anne of Austria
Charlton Heston as Cardinal Richelieu
Faye Dunaway as Milady de Winter
Christopher Lee as the Count De Rochefort
Simon Ward as the Duke of Buckingham
Raquel Welch as Constance Bonacieux
Spike Milligan as M. Bonacieux
Roy Kinnear as Planchet
Nicole Calfan as Kitty
According to George MacDonald Fraser, Richard Lester became involved with the project when the producers briefly considered casting The Beatles as the Musketeers, as Lester had directed two films with the group. The Beatles idea fell by the wayside but Lester stayed. In late 1972 he hired Fraser to write the scripts, saying he wanted to make a four-hour film and cast Richard Chamberlain as Aramis. It was later decided to turn the script into two films.
The movie was met with mostly positive reviews. Vincent Canby of The New York Times had this to say about the film: "Mr. Lester seems almost exclusively concerned with action, preferably comic, and one gets the impression after a while that he and his fencing masters labored too long in choreographing the elaborate duels. They're interesting to watch, though they are without a great deal of spontaneity."
Raquel Welch won the Golden Globe Award for Best Actress – Motion Picture Musical or Comedy for her performance. The film was nominated for the Golden Globe Award for Best Motion Picture – Musical or Comedy.
George MacDonald Fraser won the Writers' Guild of Great Britain Award for Best British Comedy Screenplay.
The film was originally intended to be an epic which ran for three hours including an intermission, but during production, it was determined the film could not make its announced release date in that form, so a decision was made to split the long epic into two shorter features, the second part becoming 1974's The Four Musketeers.
According to Ben Mankiewicz on a May 14, 2016 showing of the film on TCM, during an advanced screening, attended by the cast, after the movie ended a trailer for The Four Musketeers was shown, which none of the cast had heard anything about until then.
This incensed the actors and crew, since they were being paid for one film, and their original contracts made no mention of a second feature, resulting in lawsuits being filed to receive compensation for salaries associated with the sequel.
This led to the Screen Actor's Guild requiring all future actors' contracts to include what has become known as the "Salkind clause", which stipulates how many films are being made.
The Four Musketeers was released the following year, with footage originally intended to combine with this film's to be part of a much longer film.
In 1989, much of the cast and crew of the original returned to film The Return of the Musketeers, loosely based on Dumas' 1845 novel Twenty Years After.