A vast, starless expanse of the Delta Quadrant that Voyager began crossing in 2375, home to light-sensitive aliens and a Malon waste dumping ground.
The Void is an enormous region of space devoid of stars, which Voyager expected to need about two years to cross. Two months into the journey, shown in Night, the emptiness has worn down the crew's morale and driven Janeway into isolation in her quarters, where she broods over her decision to strand them in the Delta Quadrant.
The region is inhabited by aliens who live in darkness and are being poisoned by theta radiation that Malon freighters dump there through a vortex. Voyager allies with the natives against the Malon, collapses the vortex to stop the dumping, and leaves the Void through it before it closes.