"Trust No 1" is the sixth episode of the ninth season of the American science fiction television series The X-Files. It premiered on the Fox network on January 6, 2002. The episode was written by series creator Chris Carter and executive producer Frank Spotnitz, and directed by Tony Wharmby. "Trust No 1" helps to explore the series' overarching mythology. The episode received a Nielsen household rating of 5.1 and was viewed by 8.4 million viewers; it garnered mixed to negative reviews from television critics, with many feeling that it portrayed the series' characters in a way that was unfaithful to the show's history.

The ninth season of the American science fiction television series The X-Files commenced airing in the United States on November 11, 2001, concluded on May 19, 2002, and consists of twenty episodes. The season takes place after Fox Mulder goes into hiding, following the events of the eighth season finale, "Existence". As such, the main story arc for the season follows Dana Scully, John Doggett, and Monica Reyes on their hunt to reveal a government conspiracy involving the elaborate and malevolent creation of "Super Soldiers".