Norwegian Railways (NSB) operates a train from Oslo to Kristiansand every 3 hours. Tickets cost $40 - $60 and the journey takes 4 h 28 min. Ruter also services this route every 4 hours. Alternatively, Nettbuss Travel AS operates a bus from Oslo to Kristiansand every 3 hours. Tickets cost $55 - $70 and the journey takes 5 h. 2 other operators also service this route.
From Oslo S train to Kristiansand. 4 h 28 min kr 485. From Oslo Bussterminal bus to Kristiansand rutebilstasjon. 5 h kr 300. From Oslo drive to Kristiansand. 4 h 4 min kr 534. From Oslo Sentralstasjon [tog] train to Oslo airport, fly to Kristiansand airport, then line 35 bus to Kristiansand. 3 h 32 min kr 748.