The Gema system was an inhabited planetary system in the Delta Quadrant. In the 24th century, the Kazon-Nistrim maintained a colony on the fourth planet of this system. (VOY: "Basics, Part I")

This system was only mentioned in dialogue.
According to Star Trek: Star Charts (p. 86), this was a binary system with a F-class star and K-class star. It was located near the Tenarus Cluster.