List of unnamed asteroid belts.
Deneva system's asteroid belt
This unnamed asteroid belt was the reason why the colony of Deneva was established in the 22nd century. Freighters made regular trips carrying supplies to the asteroid belt for the miners and bringing cargo out. (TOS: "Operation -- Annihilate!")
Gamma Canaris asteroid belt
This unnamed asteroid belt contained approximately 7,000 bodies of sizes running from types "A" to "N," with approximately 34% of the bodies of atmosphere types "H" to "M." (TOS: "Metamorphosis")
Gamma Quadrant asteroid belt
This asteroid belt, located in the Gamma Quadrant near the Bajoran wormhole, was part of Miles O'Brien's and Jadzia Dax's search for the crash landed runabout USS Yangtzee Kiang in 2369. (DS9: "Battle Lines")
Pilot training
This unnamed asteroid belt, located in the Delta Quadrant, was navigated by the Delta Flyer II while Tom Paris trained Icheb and Q, Junior to pilot a starship. (VOY: "Q2")
Pursuit of Harry Mudd
This unnamed asteroid belt, located near Rigel XII, had a Schiller Rating of 3-5.
On stardate 1329.8, the USS Enterprise chased an unidentified J class vessel into this asteroid belt. After the ship overheated its engines it went adrift inside the belt, only to be destroyed after an asteroid hit the ship dead center. (TOS: "Mudd's Women")
Pursuit of Species 8472
This unnamed asteroid belt, located in the Delta Quadrant, was the location that the Hirogen pursued a lone Species 8472 bioship to make his last stand. Once in the belt, the Species 8472 held position above an asteroid and left his ship, where he was pursued. (VOY: "Prey")
Sol system asteroid belt
This unnamed asteroid belt was where Chakotay conducted part of his pilot training while in Starfleet Academy. His freshman year he took his basic flight training in North America, and then he "went to Venus for a couple of months to learn how to handle atmospheric storms and then (he) dodged asteroids for a semester in the belt. (VOY: "Future's End, Part II")