Kristín Vala Ragnarsdóttir (born 1954) is an Icelandic Earth and sustainability scientist and activist who is Professor of Sustainability Science in the Faculty of Earth Sciences and the Institute of Earth Sciences at the University of Iceland. She was the first woman to be a full professor in Earth Sciences at the University of Bristol in the UK and at the same time the first woman to become a full professor in the Science Faculty there. She was also the first woman to serve as Dean of a School at the University of Iceland.