The Nightmare is a 2015 American documentary film directed by Rodney Ascher. The film had its world premiere on January 26, 2015 at the 2015 Sundance Film Festival and focuses on the topic of sleep paralysis. Ascher chose his subject because it had happened to him in the past.The film's crew initially began approaching participants via "message groups, YouTube videos, and a half dozen books that had been written", but found that participants began approaching them after the documentary's premise was announced.