Kari Jorun Blakkisrud Hag (born April 4, 1941) is a Norwegian mathematician known for her research in complex analysis on quasicircles and quasiconformal mappings, and for her efforts for gender equality in mathematics. She is a professor emerita of mathematics at the Norwegian University of Science and Technology (NTNU).[1] With Frederick Gehring she is the author of the book The Ubiquitous Quasidisk (American Mathematical Society, 2012).[2]