Justin Marks (born April 27, 1980) is an American screenwriter, producer and television showrunner. He is best known for writing Disney's live-action remake of The Jungle Book, co-writing Top Gun: Maverick, and for creating and showrunning the Starz espionage thriller Counterpart.

One of the first scripts he penned was Street Fighter: The Legend of Chun Li for 20th Century Fox. A year prior, he had written a script for a potential He-Man film. Initially entitled Grayskull: The Masters of The Universe, the script was praised by fans yet was never used since the script was rewritten, with the film still being in development hell.

In July 2013, Marks was hired by Disney to write a live-action adaptation of The Jungle Book. Jon Favreau came on board as director, and the film was released in April 2016. In June 2015, it was revealed that Marks was working on the screenplay for a sequel to the 1986 film Top Gun. The film, titled Top Gun: Maverick, was released in theaters in May 2022, with Marks credited with co-writing the film's story with Peter Craig.

In 2016, Marks was working on a Jungle Book sequel with Favreau returning as director.

Marks created the Starz science-fiction thriller Counterpart, starring J. K. Simmons. The show was ordered straight-to-series for two 10-episode seasons. The first episode premiered December 10, 2017.

In 2020, Marks and his wife Rachel Kondo started working on the TV adaptation of Shogun, the famous novel by James Clavell. It released in 2024 to critical acclaim.