Alonis was a planet, located somewhere in the Alpha or Beta Quadrant of the galaxy. Alonis was the homeworld of an aquatic, vaguely humanoid civilization also called the Alonis.

Some Alonis served in Starfleet before their world's government became a Federation member state in the mid-24th century. (TLE novel: Serpents Among the Ruins, DS9 - Mission Gamma novel: Twilight)