Matthew Michael Carnahan is an American screenwriter who wrote the feature films The Kingdom (2007) and Lions for Lambs (2007) and is scheduled to write the film adaptation of the hit BBC television drama serial State of Play and adapt the novel, White Jazz. Carnahan wrote the screenplay for Lions for Lambs for United Artists. He is also the brother of Joe Carnahan who wrote and directed Narc and Smokin' Aces.

Critical reaction to Carnahan's work has been mixed. Based on 17 reviews, The Kingdom averaged a 55 on Metacritic. Rotten Tomatoes lists the film with 53% of critics giving the film positive reviews, based on 120 reviews. blank">Kaveh L Afrasiabi of _Asia Times Online called it "a pseudo-realist action movie that succeeds only if we degrade ourselves to adolescent Americans' perception of world affairs" and "non-stop nonsense from beginning to end." He accused the film of "FBI-worship", "Saudi-bashing", and "Islamophobia".

Lions for Lambs received generally negative to mixed reviews from critics. As of November 10, 2007 on the review aggregator Rotten Tomatoes, 27% of critics gave the film positive reviews, based on 133 reviews. On Metacritic, the film had an average score of 47 out of 100, based on 33 reviews.

Is the brother of Narc (2002) director Joe Carnahan