Gemaris V was a planet in the Alpha or Beta Quadrant. The planet was also known simply as Gemaris.
Charles and Morgan Lefler were briefly assigned to Gemaris V by Starfleet in 2359 to conduct plasma studies, and were accompanied by their daughter, Robin. (NF short story: "Lefler's Logs")
In 2366, Starfleet Captain Jean-Luc Picard mediated a dispute between the Gemarians and the Dachlyds. During this process, Picard exhausted himself but managed to find a middle ground for both peoples, despite the fact both sides were thought of as stubborn. (TNG episode: "Captain's Holiday")