Thomas Mason is a Canadian-American[1] condensed-matter physicist who serves as the director of Los Alamos National Laboratory.

Prior to this appointment, he had been an executive at Battelle Memorial Institute from 2017 to 2018, and the director of Oak Ridge National Laboratory from 2007 to 2017.

[2] Mason moved to Oak Ridge in 1998 at the start of construction of the Spallation Neutron Source[3] which he led from 2001 until project completion in 2006.

[8] He stepped down from the position in 2017 to serve as the senior vice president for laboratory operations at Battelle Memorial Institute.

[9] Mason became director at Los Alamos as part of the new Triad National Security LLC management team.