The Rashanar sector was an area of space located in the Alpha Quadrant near the Cardassian Union. The Rashanar sector had at least one inhabited planet in the region, Ontail, which was inhabited by the Ontailians.
In 2375, the Rashanar sector was the location of the disastrous Battle of Rashanar between Federation Alliance and Dominion forces in the closing stages of the Dominion War. All ships were lost in the battle, and the wreckages were held in place by a huge gravity sink in what became known as the "boneyard". (TNG novels: A Time to Be Born, A Time to Die)