Leonard Joseph "Chico" Marx was an American comedian, actor and pianist. He was the oldest brother in the Marx Brothers comedy troupe, alongside his brothers Arthur ("Harpo"), Julius ("Groucho"), Milton ("Gummo") and Herbert ("Zeppo"). His persona in the act was that of a charming, uneducated but crafty con artist, seemingly of rural Italian origin, who wore shabby clothes and sported a curly-haired wig and Tyrolean hat. On screen, Chico is often in alliance with Harpo, usually as partners in crime, and is also frequently seen trying to con or outfox Groucho. Leonard was the oldest of the Marx Brothers to live past early childhood, the first-born being Manfred Marx who had died in infancy. In addition to his work as a performer, he played an important role in the management and development of the act in its early years.

The Marx Brothers were an American family comedy act that was successful in vaudeville, on Broadway, and in 14 motion pictures from 1905 to 1949. Five of the Marx Brothers' fourteen feature films were selected by the American Film Institute (AFI) as among the top 100 comedy films, with two of them, Duck Soup (1933) and A Night at the Opera (1935), in the top fifteen. They are widely considered by critics, scholars and fans to be among the greatest and most influential comedians of the 20th century. The brothers were included in AFI's 100 Years... 100 Stars list of the 25 greatest male stars of Classical Hollywood cinema, the only performers to be included collectively.