Thomas Leo McCarey (October 3, 1898 – July 5, 1969) was an American film director, screenwriter, and producer. He was involved in nearly 200 films, including the critically acclaimed Duck Soup, Make Way for Tomorrow, The Awful Truth, Going My Way, The Bells of St. Mary's, My Son John, and An Affair to Remember.

While focusing mainly on screwball comedies during the 1930s, McCarey turned towards producing more socially conscious and overtly religious films during the 1940s, ultimately finding success and acclaim in both genres. McCarey was one of the most popular and established comedy directors of the pre-World War II era.

Born in Los Angeles, California, McCarey attended St. Joseph's Catholic School and Los Angeles High School. His father was Thomas J. McCarey, whom the Los Angeles Times called "the greatest fight promoter in the world." Leo McCarey would later make a boxing comedy with Harold Lloyd called The Milky Way (1936).

McCarey graduated from the University of Southern California law school and besides the law tried mining, boxing, and songwriting before becoming an assistant director to Tod Browning in 1919. It was McCarey's boyhood friend, the actor and future fellow director David Butler, who referred him to Browning. Browning convinced McCarey, despite his photogenic looks, to work on the creative side as a writer rather than as an actor. McCarey then honed his skills at the Hal Roach Studios. Roach had hired him as a gagman in 1923, after McCarey had impressed him with his sense of humor following a handball game at a sports club.

McCarey initially wrote gags for the Our Gang series and other studio stars, then produced and directed shorts including two-reelers with Charley Chase. Chase would, in fact, become McCarey's mentor. Upon the comedian's death in 1940, McCarey was quoted as saying, "Whatever success I have had or may have, I owe to his help because he taught me all I know." The two men were especially compatible, as they both enjoyed a side hobby trying to write popular songs.

While at Roach, McCarey, according to later interviews, cast Stan Laurel and Oliver Hardy together and guided development of their onscreen characters, thus creating one of the most enduring comedy teams of all time. He only officially appeared as director of the duo's shorts We Faw Down (1928), Liberty (1929) and Wrong Again (1929), but wrote many screenplays and supervised the direction by others. By 1929, he was vice-president of production for the studio. Less well known from this period are the shorts he directed with Max Davidson when Roach put together the Irish-American McCarey with the Jewish-American actor for a series of "dialect comedies." They were rediscovered in recent years after their 1994 exhibition at the Giornate del Cinema Muto in Pordenone Italy.

In the sound era, McCarey focused on feature film direction, working with many of the biggest stars of the era including Gloria Swanson (Indiscreet, 1931), Eddie Cantor (The Kid From Spain, 1932), the Marx Brothers (Duck Soup, 1933), W.C. Fields (Six of a Kind, 1934), and Mae West (Belle of the Nineties, 1934). A series of six films at Paramount came to a crashing halt with his production of Make Way for Tomorrow in 1937. While the story of an elderly couple who have to be separated for economic and family reasons during the Depression was not without humor in its treatment, the results were too unpopular at the box office and the director was let go. Nonetheless, the film was recognized early on for its importance by being selected for the permanent collection of the recently formed Museum of Modern Art in New York City. In later years it became canonical, and even considered by some as McCarey's masterpiece, due to perceptive champions such as Bertrand Tavernier, Charles Silver and Robin Wood.

Invited to Columbia later in 1937, McCarey earned his first Academy Award for Best Director for The Awful Truth, with Irene Dunne and Cary Grant. It was a screwball comedy that launched Grant's unique screen persona, largely concocted by McCarey (Grant copied many of McCarey's mannerisms).^{[citation needed]} Along with the similarity in their names, McCarey and Cary Grant shared a physical resemblance, making mimicking McCarey's intonations and expressions even easier for Grant. As writer/director Peter Bogdanovich notes, "After The Awful Truth, when it came to light comedy, there was Cary Grant and then everyone else was an also-ran." ^{[citation needed]}