After finishing high school, Lang briefly attended the Technical University of Vienna, where he studied civil engineering and eventually switched to art. In 1910 he left Vienna to see the world, traveling throughout Europe and Africa and later Asia and the Pacific area. In 1913, he studied painting in Paris, France. The next year, he returned home to Vienna at the outbreak of the First World War. In January 1914, he was drafted into service in the Austrian army and fought in Russia and Romania during World War I, where he was wounded three times.
His writing stint was brief, as Lang soon started to work as a director at the German film studio Ufa, and later Nero-Film, just as the Expressionist movement was building. In this first phase of his career, Lang alternated between art films such as Der Müde Tod (Destiny, literally "Tired Death") and populist thrillers such as Die Spinnen (Spiders), combining popular genres with Expressionist techniques to create an unprecedented synthesis of popular entertainment with art cinema. In 1920, he met his future wife, the writer and actress Thea von Harbou. She and Lang co-wrote the scripts for 1922's Dr. Mabuse, der Spieler (Dr. Mabuse the Gambler), which ran for four hours in two parts in the original version and was the first in the Dr. Mabuse trilogy, 1924's Die Nibelungen, the famed 1927 masterpiece Metropolis, and the 1931 classic, M, his first "talking" picture.
Although some consider Lang's work to be simple melodrama, he produced a coherent oeuvre that helped to establish the characteristics of film noir, with its recurring themes of psychological conflict, paranoia, fate and moral ambiguity. His work influenced filmmakers as disparate as Jacques Rivette and William Friedkin.
In 1931, between Metropolis and Das Testament des Dr. Mabuse, Lang directed what many film scholars consider to be his masterpiece: M, a disturbing story of a child murderer (Peter Lorre in his first starring role) who is hunted down and brought to rough justice by Berlin's criminal underworld. M remains a powerful work; it was remade in 1951 by Joseph Losey, but this version had little impact on audiences, and has become harder to see than the original film.
Lang epitomized the stereotype of the tyrannical German film director such as Erich von Stroheim and Otto Preminger; he was known for being hard to work with. During the climactic final scene in M, he allegedly threw Peter Lorre down a flight of stairs in order to give more authenticity to Lorre's battered look. He even wore a monocle that added to the stereotype.
The problem is that many portions of the story cannot be checked, and of those that can, most are contradicted by the evidence: Lang actually left Germany with most of his money, unlike most refugees, and made several return trips later in the same year. There were of course no witnesses to the meeting besides Goebbels and Lang, but Goebbels's appointment books, when they refer to the meeting, mention only the banning of Testament. No evidence has been discovered in any of Goebbels's writings to affirm the suggestion that he was planning to offer Lang any position. Jean-Luc Godard's film Contempt (1963), in which Lang appeared as himself, presents a bare outline of the story as fact.
Whatever the truth of this story, it is known that Lang did in fact leave Germany in 1934 and moved to Paris, where he filmed a version of Ferenc Molnar's Liliom, starring Charles Boyer. This was Lang's only film in French (not counting the French version of Testament). He then went to the United States. Lang's wife Thea von Harbou, who had started to sympathize with the Nazis in the early 1930s and joined the Nazi party (the NSDAP) in 1932, stayed behind. The two were divorced in 1933.
Upon his arrival in Hollywood, Lang joined the MGM studio and directed the crime drama Fury. He became a naturalized citizen of the United States in 1939. Lang made twenty-one features in the next twenty-one years, working in a variety of genres at every major studio in Hollywood, occasionally producing his films as an independent. These films, often compared unfavourably by contemporary critics to Lang's earlier works, have since been reevaluated as being integral to the emergence and evolution of American genre cinema, film noir in particular. One of his most famous film noirs is the police drama The Big Heat (1953), noted for its uncompromising brutality, especially for a scene in which Lee Marvin throws scalding coffee on Gloria Grahame's face. During this period, his visual style simplified (owing in part to the constraints of the Hollywood studio system) and his worldview became increasingly pessimistic, culminating in the cold, geometric style of his last American films, While the City Sleeps (1956) and Beyond a Reasonable Doubt (1957).
Fearing that Brauner would proceed with or without his assent, Lang abandoned his plans for retirement and returned to Germany in order to make his Indian Epic, which is regarded as a masterpiece by a number of film scholars today. Following the production, Brauner was ready to proceed with his remake of Das Testament des Doctor Mabuse when Lang approached him with the idea of adding another original film to the series. The result was The Thousand Eyes of Dr. Mabuse (1960), made in a hurry and with a relatively small budget. It can be viewed as the marriage between the director's early experiences with expressionist techniques in Germany as well as the spartan style already visible in his late American work. Lang was approaching blindness during the production, making it his final project.
Returning to the United States in retirement, he continued collecting research material and drafting screenplays, though he never made another film. While his career had ended without fanfare, his American and later German works were championed by the critics of the Cahiers du Cinema. One Cahiers critic, Jean-Luc Godard, became a film director and cast Lang in Contempt (1963), in addition to considerable critical adulation in the U.S. from critics such as Peter Bogdanovich.