Lawrence G. DiTillio (February 15, 1948 – March 16, 2019) was an American film, TV series, and tabletop role-playing game writer. His creations include He-Man and She-Ra: The Secret of the Sword and the award-winning Masks of Nyarlathotep.

Larry DiTillio attended the film school at New York University for four years. He then spent an additional two years at UCLA's film school.^[1]

After graduating, DiTillio decided to make a career as a Hollywood writer. He knocked on agency doors until he was able to find an agent willing and able to find him work as a film writer.^[1] DiTillio wrote for both television and movies in the 1970s, including a stint on Filmation's Fat Albert and the Cosby Kids. He then became a staff writer for the original He-Man and the Masters of the Universe series and over its two seasons, wrote 17 episodes, more than anyone else. He also directed one episode.

During a writers' strike in 1983, DiTillio searched for other ways to generate income through writing, so he was hired by Flying Buffalo.^[2]: 37 DiTillio wrote The Isle of Darksmoke (1984), the final multiplayer Tunnels & Trolls adventure that Flying Buffalo published.^[2]: 38 DiTillio also collaborated with Lynn Willis to create the world-spanning campaign Masks of Nyarlathotep (1984) for Chaosium's Call of Cthulhu, which author Shannon Appelcine states is considered one of the best roleplaying adventures of all time,^[2]: 86 and won an Origins Award.^[3] For a few months, DiTillio was also a contributor to Chaosium's Different Worlds magazine, writing about news from the world of film and television in his "The Sword of Hollywood" column.^[4] Other Chaosium titles he wrote or contributed to, include; The Grey Knight, the first adventure for the Pendragon role-playing game, Demon Magic: The Second Stormbringer Companion for the Stormbringer fantasy role-playing game, and the Call of Cthulhu supplement Terror Australis.^[5]

Despite his success in the role-playing games industry, once the screenwriters' strike ended, DiTillio went back to screenwriting.^[6]

In 1985, he wrote the feature-length film He-Man and She-Ra: Secret of the Sword. Following its release, he and J. Michael Straczynski became writers for Filmation's spin-off show She-Ra: Princess of Power.^[1] DiTillio created the show bible for the spinoff show and invented most of the character names.^{[7][page needed]} Straczynski later recalled the considerable time DiTillio spent writing character background for the show. "One of the things Larry and I decided, very early on, was that She-Ra couldn't just be 'He-Man with boobs.' The show had to go deeper than that, especially given that we were creating this for a female lead character."^[1] However, when Filmation refused to give them credit on-screen, both left, finding work with DIC Entertainment on Jayce and the Wheeled Warriors.

In 1993, DiTillio worked with Straczynski again, this time on the science-fiction series Babylon 5, with Straczynski as producer and DiTillio the executive story editor.^[6][2]: 41 DiTillio also worked on the animated series Beast Wars, writing or co-writing most of the episodes.^[2]: 41 In 2002, he was a writer for the updated He-Man and the Masters of the Universe series.

DiTillio died at the age of 71 on March 16, 2019.^[1]