Asahan Regency is a regency in North Sumatra. Following the creation of the new Batubara Regency (which was carved out of Asahan Regency on 15 June 2007), the regency now covers an area of 3,675.79 square kilometres and according to the 2010 census had a population of 667,563 people. Its seat is Kisaran. The Regency surrounds but does not include the city of Tanjung Balai which was formerly its capital.