Sululluub was a field of asteroids that circled the star Sullust within the Sullust system. This asteroid field resided in the Brema sector, which is part of the Outer Rim Territories, and is considered an asteroid field according to legend and orbited the star.
Just prior to the Battle of Yavin, Imperial TIE fighters were dispatched to scour the asteroid belt, seeking out any Rebels that might be hiding there.