"This Side of Paradise" is the twenty-fourth episode of the first season of the original science fiction television series, Star Trek. It was first broadcast on March 2, 1967, and was repeated on August 10, 1967. The episode was written by D. C. Fontana and Jerry Sohl (using the pseudonym Nathan Butler), and directed by Ralph Senensky. The title is taken from the poem "Tiare Tahiti" by Rupert Brooke and the novel "This Side of Paradise" by F. Scott Fitzgerald.

In this episode, the USS Enterprise visits a planet where the inhabitants are under the influence of strange plant life.

Enterprise is ordered to a Federation colony on Omicron Ceti III. Shortly after the colony was founded some years prior, it was discovered the planet was bathed in Berthold rays, a lethal form of radiation. Having lost communications with the colony recently and fearing the colonists deceased, the Federation wants the Enterprise crew to recover the colonists and their equipment.

The ship arrives in orbit, and Captain Kirk, along with First Officer Spock, Chief Medical Officer Leonard McCoy and others beam down to the colony. They are surprised to find the colonists all alive and well in a paradise-like setting. Their leader, Elias Sandoval, welcomes them and explains they only lost communications due to equipment failure. Sandoval and other colonists allow McCoy to examine them, who not only sees them in perfect health but is surprised to find Sandoval has a healthy appendix despite having it removed before leaving for the colony. Kirk orders the away team to learn more about the colony. They notice the lack of any animal life including those brought with them to the colony, which Sandoval explains away by saying that they have adopted vegetarianism to sustain themselves.

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