Dark Skies is an American UFO conspiracy theory–based science fiction television series. It debuted on NBC on September 21, 1996, and ended on May 31, 1997, and was later rerun by the Sci-Fi Channel; 18 episodes and a two-hour pilot episode were broadcast as a part of NBC's short-lived "Thrillogy" block. The success of The X-Files on Fox resulted in NBC commissioning this proposed competitor following a pitch from producers Bryce Zabel and Brent Friedman. The series tagline was "History as we know it is a lie."