Matthew Michael Carnahan (sometimes credited as Matt Carnahan) is an American scriptwriter. Among his numerous works are screenplays for The Kingdom (2007); the film adaptation of the hit BBC television drama serial State of Play; and Lions for Lambs for United Artists. He also worked on the zombie film World War Z (2013). He wrote the screenplay for the feature film Dark Waters (2019), based on a 2016 feature article about industrial pollution in The New York Times magazine.