John L. Balderston (October 22, 1889, in Philadelphia – March 8, 1954, in Los Angeles) was an American playwright and screenwriter best known for his horror and fantasy scripts.
Balderston began his career as a journalist in 1912 while still a student at Columbia University; he worked as the New York correspondent for the Philadelphia Record. He worked as European war correspondent during World War I for the McClure Newspaper Syndicate, then was director of information in England and Ireland for the US Committee on Public Information. In the early 1920s he was the editor of Outlook magazine in London and then head of the London bureau for the New York World.
Balderston achieved success as a playwright in 1926 with the London production of his play Berkeley Square which he had written with Jack Squire, the editor of The London Mercury. In 1927, he was retained by Horace Liveright to revise Hamilton Deane's stage adaptation of Dracula for its American production. This subsequently formed the basis of the 1931 film version, leading Balderston into a screenwriting career, initially for Universal Pictures horror films: in addition to Dracula, he contributed to Frankenstein, Bride of Frankenstein, The Mummy, and Dracula's Daughter.
Balderston spent much of his career adapting novels for the screen, including The Prisoner of Zenda in 1937 and 1944's Gaslight, which earned him his second Academy Award nomination (the first was for 1935's The Lives of a Bengal Lancer). He was also one of the team of writers who collaborated on the 1939 film adaptation of Gone with the Wind.