Frier or Frierfjord is a fjord in Telemark county, Norway. The 14-kilometre (8.7 mi) long fjord is located along the Skaggerak coast in the traditional district of Grenland and it forms the border with the municipalities of Bamble, Skien, and Porsgrunn. The fjord is actually an inner arm of the Langesundsfjord, and historically this fjord was also known as the Langesundsfjord. The fjord stretches from the opening to Langesundsfjord in the south to the mouth of the Porsgrunn River in the north. The much smaller fjord of Gunneklevfjord opens into the Porsgrunn/Skien River and is separated from Frierfjorden by the peninsula of Herøya.