The Alpha Leonis system was an inhabited planetary system in the Beta Quadrant. Notable forms of life in this system included the eel-birds of Regulus V and the Regulan bloodworms of Regulus II. (TOS: "The Cage", "The Menagerie, Part I"; TNG: "The Vengeance Factor"; Star Trek VI: The Undiscovered Country, production art; TOS: "Amok Time"; ENT: "Two Days and Two Nights") The system was located three hundred light years from the Bajoran system. (DS9: "Fascination")
In 2154, a Vulcan High Command attack fleet massed in this system in preparation for an abortive preemptive strike against the Andorians. Regulus was the closest accessible star known to be outside the maximum range of Andorian Imperial Guard listening posts. (ENT: "Kir'Shara")
In 2293, the location of Regulus in the Milky Way Galaxy was labeled in a star chart that was in Captain James T. Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country, okudagram)
|Alpha Leonis system|
|Regulus • Regulus II • Regulus III • Regulus V|
According to Star Trek: Star Charts (pp. 56,61,62, "United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), in the late 24th century, the system was a destination on the major space lanes. The planets Regulus III and Regulus V were listed as Federation members.