"One Breath" is the eighth episode of the second season of the American science fiction television series The X-Files. It premiered on the Fox network on November 11, 1994. It was written by Glen Morgan and James Wong, directed by R. W. Goodwin, and featured guest appearances by Melinda McGraw, Sheila Larken and Don S. Davis. The episode helped to explore the series' overarching mythology. "One Breath" earned a Nielsen household rating of 9.5, being watched by 9.1 million households in its initial broadcast. The episode received mostly positive reviews from television critics.

The show centers on FBI special agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) who work on cases linked to the paranormal, called X-Files. In the episode, Scully is found comatose in hospital after her abduction in the earlier episode "Ascension". Mulder attempts to investigate what has happened to her, but finds himself hindered by a man he had believed to be an ally.

Anderson returned to the series only days after having given birth, missing the previous episode due to her pregnancy. Morgan and Wong attempted to create a version of the earlier episode "Beyond the Sea", this time centered on Duchovny's character Mulder. The episode also introduced the character of Melissa Scully, an attempt to provide a romantic lead for Mulder which was later dropped.