Kenneth Lonergan is an American film director, playwright, and screenwriter. He is the co-writer of the film Gangs of New York (2002), and wrote and directed You Can Count on Me (2000), Margaret (2011), and Manchester by the Sea (2016). Lonergan is also known for his work as a playwright. His most noted plays include This Is Our Youth, Lobby Hero and The Waverly Gallery. Each also had a successful revival engagement on Broadway, which resulted in each play receiving a nomination for the Tony Award for Best Revival of a Play.

Gangs of New York is a 2002 American historical drama film directed by Martin Scorsese and written by Jay Cocks, Steven Zaillian, and Kenneth Lonergan, based on Herbert Asbury's 1927 book The Gangs of New York. The film stars Leonardo DiCaprio, Daniel Day-Lewis, and Cameron Diaz, along with Jim Broadbent, John C. Reilly, Henry Thomas, Stephen Graham, Eddie Marsan, and Brendan Gleeson in supporting roles.