According to the Internet Movie Database, and the book “Film Facts” by Patrick Robertson (formerly called “The Guinness Book of Movie Facts & Feats”), that record is held by Tom London.
Born Leonard Clapham in Louisville, KY, on August 24, 1889, he was a salesman who eventually wound up working for the Selig Polyscope Film Company in Chicago. (Since there is some confusion about his year of birth, we confirmed that it was 1889 through his Social Security records.) Around 1910 Leonard went with the company when it moved to California, and before long he began playing small parts in the westerns being made by the Selig Company. His expertise with horses quickly lead to bigger roles, and by the time he died in North Hollywood, CA, on December 5, 1963, it is estimated that he had played characters in well over 500 features. The Internet Movie Database lists him in 558 movies (silent and sound), while “Film Facts” estimates that he had been in over 2,000 movies. (We’ll go with the number 558, since to have made over 2,000 movies would require that he had made 30 to 40 feature films a year each year for his entire career!)
Although Tom London appeared in other types of films, “All Quiet on the Western Front” (1930) and “Platinum Blonde” (1931) for example, westerns were his true medium. He has been identified in nearly 500 sound films, which includes work in at least 52 serials and 320 westerns. He typically played a sheriff, ranch owner or bad guy, and in non–westerns a policeman. Leonard Clapham adopted the stage name “Tom London” in 1924. It is stated by a number of sources that he was in the 1903 movie “The Great Train Robbery”. If that is true, he was only 14 when he was an extra in that film.
With that said, the person who has physically been in the most movies is undoubtedly Bess Flowers (1898–1984). Known to some as “Queen of the Hollywood Extras”, Bess was rarely listed in a films’ credits and almost never spoke a line. But between 1923 and 1964 it is estimated that she appeared in well over 700 feature films including such classics as “It Happened One Night” (1934), “My Man Godfrey” (1936), “Double Indemnity” (1944), and “All About Eve” (1950). Although she was usually in the background, often playing a wealthy matron, her face is probably familiar to anyone who has seen a lot of vintage movies.