Citizen Kane is a 1941 American drama film produced by, directed by, and starring Orson Welles. He also co-wrote the screenplay with Herman J. Mankiewicz. The picture was Welles' first feature film. Citizen Kane is frequently cited as the greatest film ever made. For 50 consecutive years, it stood at number 1 in the British Film Institute's Sight & Sound decennial poll of critics, and it topped the American Film Institute's 100 Years ... 100 Movies list in 1998, as well as its 2007 update. The film was nominated for Academy Awards in nine categories and it won for Best Writing (Original Screenplay) by Mankiewicz and Welles. Citizen Kane is praised for Gregg Toland's cinematography, Robert Wise's editing, Bernard Herrmann's music, and its narrative structure, all of which have been considered innovative and precedent-setting.

The quasi-biographical film examines the life and legacy of Charles Foster Kane, played by Welles, a composite character based on American media barons William Randolph Hearst and Joseph Pulitzer, Chicago tycoons Samuel Insull and Harold McCormick, as well as aspects of the screenwriters' own lives. Upon its release, Hearst prohibited the film from being mentioned in his newspapers.

After the Broadway success of Welles's Mercury Theatre and the controversial 1938 radio broadcast "The War of the Worlds" on The Mercury Theatre on the Air, Welles was courted by Hollywood. He signed a contract with RKO Pictures in 1939. Although it was unusual for an untried director, he was given freedom to develop his own story, to use his own cast and crew, and to have final cut privilege. Following two abortive attempts to get a project off the ground, he wrote the screenplay for Citizen Kane, collaborating with Herman J. Mankiewicz. Principal photography took place in 1940, the same year its innovative trailer was shown, and the film was released in 1941.

Although it was a critical success, Citizen Kane failed to recoup its costs at the box office. The film faded from view after its release, but it returned to public attention when it was praised by French critics such as André Bazin and re-released in 1956. In 1958, the film was voted number 9 on the prestigious Brussels 12 list at the 1958 World Expo. Citizen Kane was selected by the Library of Congress as an inductee of the 1989 inaugural group of 25 films for preservation in the United States National Film Registry for being "culturally, historically, or aesthetically significant".