Eystein Jansen (born 28 February 1953, Bergen) is a Norwegian professor in marine geology and paleoceanography at the University of Bergen and researcher and adviser at the Bjerknes Centre for Climate Research (BCCR).
He headed the Bjerknes Centre from its founding in 2000 to 2013.
He is currently a member of the Scientific Council of the European Research Council, and the Academic Director of the Academia Europaea Bergen Knowledge Hub.
Jansen earned an MSc degree in 1981 and a PhD degree (dr.scient.) in 1984 from the University of Bergen.
He was assistant and later associate professor in marine geology at the university 1985–1993 and became a full professor in 1993.He was a co-ordinating lead author for the paleoclimate chapter of the IPCC Fourth Assessment Report and was one of the lead authors of the IPCC Fifth Assessment Report.