Vest-Agder (Norwegian: [ˈvɛ̂stˌɑɡdər] (listen); "West 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.
Vest-Agder was a major source of timber for Dutch and later English shipping from the 16th century onwards. Historically, the area exported timber, wooden products, salmon, herring, ships, and later nickel, paper, and ferrous and silica alloys. Compared to other counties of Norway, today's exports-intensive industry produces shipping and offshore equipment (National Oilwell Varco), cranes (Cargotec), ships (Umoe Mandal, Flekkefjord Slip), wind turbine equipment, nickel (Glencore), and solar industry microsilica (Elkem). A major tourist attraction is Kristiansand Dyrepark.
Vest-Agder grew to political prominence with the decision of King Christian IV to establish Kristiansand as a key naval base, trading centre, and bishopric in 1641, forcing urban citizens and merchants from all over Agder to settle in the city. The county had large-scale emigration to North America from the 1850s onwards.