Aust-Agder was a county in Norway from 1 January 1919 to 31 December 2019, after it was merged with Vest-Agder to form Agder county. In 2002, there were 102,945 inhabitants, which was 2.2% of Norway's population. Its area was 9,212 square kilometres. The county's administrative center was the town of Arendal.