The Princeton Site Office (PSO) is an organization within the U.S. Department of Energy's Office of Science with responsibility to oversee and manage the Management and Operating (M&O) contract for the Princeton Plasma Physics Laboratory (PPPL) in Princeton, New Jersey.

PPPL is one of ten Office of Science Laboratories with a primary mission on delivering breakthrough science and technology in the areas of Fusion and Plasma Research. The PSO is responsible for program implementation, acquisition management, and laboratory stewardship at PPPL. Through its oversight role, the PSO is affecting the safe and efficient operation of PPPL while enabling the pursuit of visionary research and development in support of DOE's missions.