The Vintaak system is a star system that in the mirror universe is located deep in Tholian space, and possesses at least one gas giant.
In the mirror universe year 2155, Commander Jonathan Archer discovered that a starship from the future was being held inside an asteroid in the Vintaak system. After successfully staging a mutiny against Captain Forrest, Archer commandeered and forced the Terran Empire starship ISS Enterprise to the Vintaak system in order to retrieve the captured ship. Though Forrest eventually regained command of the Enterprise, Archer had locked the helm controls on course for Vintaak. Forrest's attempts to change Enterprise's course ultimately proved futile.
When an away team under Archer's command beamed aboard the future starship, the USS Defiant, the Enterprise was attacked and captured in a Tholian web. Most of the Enterprise's crew was able to escape in escape pods, but the ship itself was destroyed. (ENT: "In a Mirror, Darkly")
It is unknown if this system is located inside Tholian space in the regular universe too, though it most likely at least exists there, as in mirror universe episodes it is always suggested that while political entities may be different, at least stellar cartography corresponds between both universes. The regular universe Vintaak system might be close to the region of space where the Defiant disappeared as it was close to where it reappeared in the mirror universe, though since there was a temporal shift perhaps a spacial shift also occurred.