The Thomas Jefferson Site Office (TJSO) 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 Thomas Jefferson National Accelerator Facility (TJNAF) in Newport News, Virginia.

TJNAF is one of ten Office of Science Laboratories and is a single program laboratory with a primary mission on delivering breakthrough science and technology in the area of Nuclear Physics.

The TJSO is responsible for program implementation, acquisition management, and laboratory stewardship at TJNAF. Through its oversight role, the TJSO is affecting the safe and efficient operation of TJNAF while enabling the pursuit of visionary research and development in support of DOE's missions.