System J-25 was a planetary system that had at least six planets, located outside Federation space. As of 2365, the nearest Federation starbase to this system was Starbase 185; a Galaxy-class starship would require two years and seven months to reach it from J-25.
In 2365, the Borg still had a presence in the system. A Borg cube detected the Federation starship USS Enterprise-D when it was transported to this system by Q in 2365. Shortly afterward, the cube attacked the Enterprise and pursued it across the system before the Starfleet vessel was rescued by Q.