"The Unnatural" is the 19th episode of the sixth season of the American science fiction television series The X-Files, which first aired on April 25, 1999, on the Fox network. Written and directed by lead actor David Duchovny, the episode is unconnected to the wider mythology of The X-Files, and functions as a "Monster-of-the-Week" story. "The Unnatural" earned a Nielsen household rating of 10.1, and its first broadcast was watched by 16.88 million people. The episode received positive reviews from critics, and was well-liked by members of the cast and crew, including series creator Chris Carter and co-star Gillian Anderson.