Entelior is a star system in the Alpha Quadrant with at least four planets, including Entelior III and Entelior IV. Entelior is near Tzenkethi space and the Temecklia star system.
In 2317, Demora Sulu was to take Strolt to the Entelior star system to rendezvous with Zeeren. (ST - Tales from the Captain's Table short story: "Iron and Sacrifice")
In 2362, the USS Okinawa and the USS Assurance discovered bilitrium on several planets in the Entelior system. Due to the Tzenkethi War, the Okinawa and the Assurance were forced to engage the Tzenkethi to stop them from claiming the system as their own and taking possession of the bilitrium. (ST - Typhon Pact novel: Rough Beasts of Empire)