The Oak Ridge National Laboratory Site Office (OSO) 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 Oak Ridge National Laboratory (ORNL) and the Oak Ridge Institute for Science and Education (ORISE) in Oak Ridge, Tennessee.

ORNL is one of ten Office of Science Laboratories and is a multi-program laboratory with a primary mission on delivering breakthrough science and technology in the areas of neutron science, energy, high-performance computing, systems biology, materials science, and national security. ORISE creates and promotes collaborative partnerships among academia, government and industry to strengthen the nation’s scientific research and education enterprise. The OSO is responsible for program implementation, acquisition management, and laboratory stewardship at ORNL and ORISE. Through its oversight role, the OSO is affecting the safe and efficient operation of ORNL and ORISE while enabling the pursuit of visionary research and development in support of DOE's missions.