The Gamma Quadrant is the common designation for one quarter of the Milky Way Galaxy. Its boundary is defined by a meridian passing through the galactic core and the Sol system, and a second meridian perpendicular at the core. Its closest point to Earth is located approximately 30,000 light years away. However, the stable Bajoran wormhole links the Idran system in the Gamma Quadrant with the Bajoran system in the Alpha Quadrant.
It is believed the Hur'q originated from the quadrant.
The Vulcans were at the forefront of the exploration of the Quadrant, beginning only months after the wormhole was discovered by Benjamin Sisko and Jadzia Dax in 2369. Within three years, the Vulcans made many discoveries, including the remains of the Hur'q race.
The Klingons showed an interest in exploring the Gamma Quadrant shortly after its discovery by sending their own scout ships to the quadrant. The IKS Toh'Kaht was among the first ships to explore the quadrant in an effort to establish colonies on the other side of the wormhole. They also operated freighter to the quadrant.
The Ferengi saw the Gamma Quadrant as an enormous chance to make a profit and their reputations would be, as Gral put "absolutely stainless".
A large portion of the Gamma Quadrant was under the control of the Dominion, but it is believed that some minor powers exist on the fringes of their space.
In the act directly precipitous to the Dominion War, the Federation mined the entrance to the wormhole (leading to the Gamma Quadrant) in 2373. This cut off access to this quadrant from any Alpha Quadrant powers and prevented Dominion reinforcements from adding to the Dominion War.