System J-25 was a planetary system that had at least six planets. It was located more than 7,000 light years from Starbase 185 of the United Federation of Planets, the closest starbase in the 24th century.

The sixth planet was class M and previously inhabited by an intelligent species.

In the 24th century, the Borg had a presence in the system. A Borg cube scout detected the Federation starship USS Enterprise-D when it was transported to this system by Q in 2365. Shortly after, the Enterprise-D made first contact.

Guinan was familiar with the area of space in which System J-25 was located. (TNG: "Q Who")

According to Star Trek: Star Charts (p. 13) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), System J-25 (FGC-J25) was located in the Beta Quadrant. The system's primary was an A-class star. This system was located near the Borg transwarp network.