How many seasons did the original series run? Star Trek: The Original Series ran for three seasons. The first season aired from 1966 to 1967, the second from 1967 to 1968, and the third from 1968 to 1969. Across those seasons, the series produced 79 regular episodes, in addition to the original pilot “The Cage.”
The show’s three-season run was shorter than the five-year mission described in its opening narration. NBC canceled the series after the third season, following declining ratings and difficult scheduling. The network moved the final season to Friday nights at 10 p.m., a time slot that made it harder for the young audience to watch.
Fans organized a substantial letter-writing campaign to save the program, helping secure the third season after the second. Although the series ended in 1969, reruns in syndication introduced it to a much larger audience. Its popularity led to the animated series in the 1970s and eventually to a feature-film revival beginning with “Star Trek: The Motion Picture” in 1979.