Overview of the Alpha-Beta Quadrants
The Valt system was an inhabited planetary star system in the territory of the Klingon Empire, located within the Beta Quadrant. The system consisted of the primary Valt and the inhabited planet Valt Minor. This was the homeworld of the Valtese. (TNG: "The Perfect Mate")
In 2256, this star's location was labeled on the star chart "Alpha/Beta Quadrant Overview" in the ready room aboard the USS Discovery. The star was located in the territory of the Klingon Empire. (TNG: "The Perfect Mate"; DIS: "Magic to Make the Sanest Man Go Mad", "The War Without, The War Within")
This star system was only mentioned in writing.
According to Star Trek: Star Charts (p. 62) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), Valt was a multi-system with a pair of M-class stars.