The Persephone system was a single star system in the Alpha Quadrant, named after the Greek goddess Persephone. It contained eight planets, of which at least two were inhabitable by humanoids, and the ancient comet C/2260-Quentin.
In 2259, the USS Enterprise visited the Persephone system to study the behavior of C/2260-Quentin, and prevented it from catastrophically colliding with Persephone III. (SNW: "Children of the Comet")
In 2364, the USS Enterprise-D visited the system to confer with Admiral Mark Jameson on Persephone V to seek his help with a hostage situation. (TNG: "Too Short A Season")