George Orson Welles (May 6, 1915 – October 10, 1985) was an American actor, director, producer, and screenwriter who is remembered for his innovative work in film, radio, and theatre. He is considered to be among the greatest and most influential filmmakers of all time.

While in his 20s, Welles directed high-profile stage productions for the Federal Theatre Project, including an adaptation of Macbeth with an entirely African-American cast and the political musical The Cradle Will Rock. In 1937, he and John Houseman founded the Mercury Theatre, an independent repertory theatre company that presented a series of productions on Broadway through 1941, including Caesar (1937), a modern, politically charged adaptation of Shakespeare's Julius Caesar.

In 1938, his radio anthology series The Mercury Theatre on the Air gave Welles the platform to find international fame as the director and narrator of a radio adaptation of H. G. Wells's novel The War of the Worlds, which caused some listeners to believe that a Martian invasion was in fact occurring. Although reports of panic were mostly false and overstated, they rocketed 23-year-old Welles to notoriety.

His first film was Citizen Kane (1941), which is consistently ranked as one of the greatest films ever made and which he co-wrote, produced, directed and starred in as the title character, Charles Foster Kane. Welles released twelve other features, the most acclaimed of which include The Magnificent Ambersons (1942), The Lady from Shanghai (1947), Touch of Evil (1958), The Trial (1962), Chimes at Midnight (1966) and F for Fake (1973). His distinctive directorial style featured layered and nonlinear narrative forms, dramatic lighting, unusual camera angles, sound techniques borrowed from radio, deep focus shots and long takes. David Thomson credits Welles with "the creation of a visual style that is simultaneously baroque and precise, overwhelmingly emotional, and unerringly founded in reality." He has been praised as "the ultimate auteur".^: 6 Among Welles's notable roles in films by other directors are Rochester in Jane Eyre (1943), Harry Lime in The Third Man (1949) and Cardinal Wolsey in A Man for All Seasons (1966). Welles was a lifelong lover of Shakespeare, and Peter Bogdanovich writes that Chimes at Midnight, in which Welles plays John Falstaff, is "arguably his best film, and his own personal favorite"; Joseph McBride and Jonathan Rosenbaum have called it Welles's masterpiece, and Vincent Canby wrote "it may be the greatest Shakespearean film ever made."

Welles was an outsider to the studio system and struggled for creative control on his projects early on with the major film studios in Hollywood and later in life with a variety of independent financiers across Europe, where he spent most of his career. Many of his films were either heavily edited or remained unreleased; after Welles went to South America to film the documentary It's All True, RKO cut more than forty minutes from Ambersons and added a happier ending, against his wishes. The missing footage from Ambersons has been called a "holy grail" of cinema. Welles wrote a 58-page memo to Universal about the editing of Touch of Evil, which they disregarded. In 1998, Walter Murch reedited the film according to Welles's specifications. With a development spanning almost 50 years, Welles's final film, The Other Side of the Wind, was posthumously released in 2018.

Welles had three marriages, including one with Rita Hayworth, and three children. Known for his baritone voice, Welles performed extensively across theatre, radio, and film. He was a lifelong magician, noted for presenting troop variety shows in the war years. He was a lifelong member of the International Brotherhood of Magicians and the Society of American Magicians. In 2002, he was voted the greatest film director of all time in two British Film Institute polls among directors and critics. In 2018, he was included in the list of the 50 greatest Hollywood actors of all time by The Daily Telegraph. Micheál Mac Liammóir, who played Iago in Welles's Othello, said "Orson's courage, like everything else about him, imagination, egotism, generosity, ruthlessness, forbearance, impatience, sensitivity, grossness and vision is magnificently out of proportion."