A dangerous region of plasma storms near the Cardassian border, used as a hiding place by the Maquis and the place where Voyager was taken to the Delta Quadrant.
The Badlands is a region of space near the border between the Federation and Cardassia, full of violent plasma storms and gravitational hazards. Ships risk serious damage there, which made it an ideal hiding place for the Maquis, the colonists who fought the Cardassians in the 2370s.
In Voyager's pilot episode, Caretaker, the USS Voyager under Captain Janeway is sent into the Badlands to find a Maquis ship commanded by Chakotay, on which Tuvok had been working undercover. Both ships are pulled across the galaxy by the Caretaker's array and stranded in the Delta Quadrant.
The Badlands is also a repeated location in Deep Space Nine, as Starfleet and the Cardassians chase Maquis raiders, including the forces of the former Starfleet officer Michael Eddington, through its storms.