The Fermi Site Office (FSO) is an organization within the U.S. Department of Energy's Office of Science responsible for oversight of the Management and Operating (M&O) contract for the operation of Fermi National Accelerator Laboratory (FNAL) in Batavia, Illinois.

FNAL is one of ten Office of Science Laboratories and is a High Energy Physics laboratory with a primary mission on delivering breakthrough science and technology in the area of high energy particle physics. The FSO is responsible for program implementation, acquisition management, and laboratory stewardship at FNAL. Through its oversight role, the FSO is affecting the safe and efficient operation of FNAL while enabling the pursuit of visionary research and development in support of DOE's missions.