The Rosfjord or Rosfjorden is a fjord in Lyngdal municipality in Agder county, Norway. The 12-kilometre (7.5 mi) long fjord runs from the town of Lyngdal to the North Sea in the south. The Austad peninsula lies on the east side of the fjord, with the village of Austad near the shoreline. The area surrounding the fjord was once part of the municipality of Austad from 1909 until its dissolution in 1963.