“Studio” and “Hollywood” are interestingly complex terms. “Studio” originally meant a room with abundant natural light. The first motion picture studios were large, glass-walled rooms designed for filming with natural light. The term “studio” expanded to refer to a motion picture production facility, and then it expanded again to mean a company that made motion pictures. By the late 1920s the best-known American studios were large, vertically integrated corporations that produced, distributed, and exhibited films: Paramount, MGM, Fox, Warner Bros., and RKO. Columbia, Universal, and United Artists were also considered major studios, though they owned few or no theaters, and there were smaller B-movie companies such as Monogram and Republic. “Hollywood” refers to a neighborhood north and west of downtown Los Angeles where a number of movie companies settled when they left the East Coast for California in the 1910s. This term has expanded in meaning as well; it now means all film production in the Los Angeles area, and even by synecdoche the entire American film industry. From about 1920 to 1950, film was the dominant entertainment industry in the United States, and the eight major studios firmly controlled this medium. The studios’ top executives, sometimes called “moguls” to emphasize their power, supervised thousands of employees and decided what films were made, how they were made, and how they were released. This is often called the “studio period,” or the “classic period,” or the “golden age of Hollywood.” After 1950 there was a gradual change to independent production as directors, producers, stars, and agents took over the creative aspects of filmmaking, with the studios mainly responsible for financing and distribution. Eventually, the Hollywood film studios expanded to other fields such as television, cable, music, home video, theme parks, and Internet, and they were bought or merged with larger corporations. The giant media conglomerates of the early 21st century (Disney, Time Warner, News Corp., Viacom, Comcast, and Sony) resemble the studios of old in their domination of the entertainment industry. This article will concentrate on the studio period, especially the economic and institutional histories of the eight major studios. However, since almost all of these companies still exist, and they are still called studios, some entries will discuss what happened to the American film industry and to the individual companies since the 1950s.