Mariah IV was the inhabited fourth planet in the Mariah system.
Along with Fahleena III and Ultima Thule, Mariah IV lay on the route taken by Valerian traders supplying weapons-grade dolamide to the Cardassians.
The Valerian transport ship Sherval Das visited this planet in 2369. (DS9: "Dramatis Personae")
According to the script, the pronunciation for Mariah was "muh-RYE-uh".