"Once Upon a Time" is the penultimate episode of the allegorical British science fiction TV series, The Prisoner. It was written and directed by Patrick McGoohan and sixth to be produced. It was first broadcast in the UK on ITV on Thursday 25 January 1968 and first aired in the United States on CBS on Saturday 14 September 1968.

The Prisoner is a British television series created by Patrick McGoohan, with possible contributions from George Markstein. McGoohan portrays Number Six, an unnamed British intelligence agent who is abducted and imprisoned in a mysterious coastal village after resigning from his position. The allegorical plotlines of the series contain elements of science fiction, psychological drama, and spy fiction. It was produced by Everyman Films for distribution by Lew Grade's ITC Entertainment.