The Twilight Zone (marketed as Twilight Zone for its final two seasons) is an American science fiction horror anthology television series created and presented by Rod Serling, which ran for five seasons on CBS from 1959 to 1964. Each episode presents a stand-alone story in which characters find themselves dealing with often disturbing or unusual events, an experience described as entering "the Twilight Zone," often with a surprise ending and a moral. Although predominantly science-fiction, the show's paranormal and Kafkaesque events leaned the show towards fantasy and horror. The phrase "twilight zone," inspired by the series, is used to describe surreal experiences.

The series featured both established stars and younger actors who would become much better known later. Serling served as executive producer and head writer; he wrote or co-wrote 92 of the show's 156 episodes. He was also the show's host and narrator, delivering monologues at the beginning and end of each episode. Serling's opening and closing narrations usually summarize the episode's events encapsulating how and why the main character(s) had entered the Twilight Zone.

In 1997, the episodes "To Serve Man" (directed by Richard L. Bare) and "It's a Good Life" (directed by James Sheldon) were respectively ranked at 11 and 31 on TV Guide's 100 Greatest Episodes of All Time. Serling himself stated that his favorite episodes of the series were "The Invaders" (directed by Douglas Heyes) and "Time Enough at Last" (directed by John Brahm).The Twilight Zone is widely regarded as one of the greatest television series of all time. In 2002, the series was ranked No. 26 on TV Guide's 50 Greatest TV Shows of All Time. In 2004, it was ranked No. 8 on TV Guide's Top Cult Shows Ever, moving to #9 three years later. In 2013, the Writers Guild of America ranked it as the third best-written TV series ever and TV Guide ranked it as the fourth greatest drama, the second greatest sci-fi show and the fifth greatest show of all time. And in 2016, the series was ranked No. 7 on Rolling Stone's list of the 100 greatest shows of all time.