Norwegian County Road 405 (Fv405) is a Norwegian county road which runs between from the village of Vegusdal in Birkenes municipality in Aust-Agder county in the north to the junction with the Norwegian National Road 9 in the village of Mosby in Kristiansand municipality in Vest-Agder county in the south. The road is 54.56 km long. Prior to a 2010 government reform, the road was classified as a Norwegian national road.