Mariah IV was the inhabited fourth planet in its star system.
Along with Fahleena III and Ultima Thule, Mariah IV was a stop on a route formerly 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")
This planet was only mentioned in dialogue.