Søgne is a former municipality in the old Vest-Agder county, Norway. The municipality existed from 1838 until 2020 when it was merged with the municipalities of Songdalen and Kristiansand into the "new" Kristiansand municipality in what is now Agder county. It was located in the traditional district of Sørlandet, just outside of the city of Kristiansand. The administrative centre of the municipality was the hamlet of Tangvall. Hamlets and areas in Søgne include Ausviga, Eig, Høllen, Langenes, Lohne, Lunde, Ny-Hellesund, Trysnes, Vedderheia, Ålo, and Åros.

Vest-Agder was one of 18 counties (fylker) in Norway up until 1 January 2020, when it was merged with Aust-Agder to form Agder county. In 2016, there were 182,701 inhabitants, around 3.5% of the total population of Norway. Its area was about 7,277 square kilometres (2,810 sq mi). The county administration was located in its largest city, Kristiansand.