Steven Cowley has been the Director of Princeton Plasma Physics Laboratory since 2018. The seventh director of the Lab, he is a theoretical physicist and international authority on fusion energy, as well as a Princeton professor of astrophysical sciences.

Most recently president of Corpus Christi College and professor of physics at the University of Oxford in the United Kingdom since 2016, Cowley previously was chief executive officer of the United Kingdom Atomic Energy Authority (UKAEA) and head of the Culham Centre for Fusion Energy.