Star Trek collectively refers to an American science-fiction franchise spanning six unique television series (which comprise 726 episodes) and ten feature films, in addition to hundreds of novels, computer and video games, fan stories, and other works of fiction — all of which are set within the same fictional universe created by Gene Roddenberry during the mid-1960s. Since its debut, "Star Trek" has become one of the most popular names in the history of science fiction entertainment, and one of the most popular franchises in television history.

It depicts an optimistic, almost utopian future in which humanity has largely overcome such traditional frailties and vices as racism, poverty, environmental destructiveness, intolerance, and superstition on Earth, and has united with other intelligent species in the galaxy. The central characters are members of the United Federation of Planets — who explore the galaxy, discovering new worlds and encountering new civilizations, while helping to promote peace and understanding. The protagonists of the Star Trek universe are essentially altruistic, however the paramilitary nature of the Federation Starfleet creates conflict on the organizational fringes of that universe. This conflict and other political dimensions of the stories allegorize 1960's political realities. Many of those issues (eg. imperialism, class warfare, human rights, the role of technology, etc.) still linger, which in part explains Star Trek's longevity.