Captain James T. Kirk's five-year mission in command of the USS Enterprise, the voyage of exploration chronicled in the original series.
The five-year mission was the deep-space assignment given to the Constitution-class USS Enterprise under Captain James T. Kirk, who succeeded Christopher Pike in command. Beginning around 2265, the ship was sent to explore unknown regions, seek out new life and civilizations, and act as the Federation's representative on the frontier, far from the support of starbases.
Over the course of the mission the Enterprise made first contact with many species, fought tense standoffs with the Klingons and Romulans, and encountered godlike beings, rogue computers and strange phenomena. The core crew included Spock as first officer and science officer, Leonard McCoy as chief medical officer and Montgomery Scott as chief engineer, along with Uhura, Sulu and later Chekov.
The mission ended in 2270, and the Enterprise returned to Earth for a major refit. Kirk was promoted to admiral, and the record of the voyage made him one of the most celebrated officers in Starfleet history. The mission became the model for later Enterprise crews, and it is the period covered by Star Trek: The Original Series and Star Trek: The Animated Series.