Keijo Olavi Kajantie (born 1940) is a Finnish theoretical physicist and Professor and Adjoint Scientist at the Helsinki Institute of Physics.
[1] He was Professor of Physics at the University of Helsinki from 1973 to 2008.
[2][3] From 1985 to 1990 he was a Research Professor of the Academy of Finland[4] and he has worked in the CERN Theory Division.
[5] He is best known for his contributions to the study of the electroweak and strong interactions at high temperatures, as well as to the field of ultrarelativistic nuclear collisions.
[6] His research interests include ultrarelativistic nuclear collisions, finite temperature field theory, string theory and QCD matter, cosmological phase transitions and null infinity in general relativity.