The Service de Physique Théorique (SPhT) of Saclay is a laboratory of the Direction des Sciences de la Matière (DSM) of the Commissariat à l'Energie Atomique (CEA). The laboratory is also an Unité de Recherche Associée (URA 2306) of the Département des Sciences Physiques et Mathématiques (SPM) of the Centre National de la Recherche Scientifique (CNRS).

The SPhT has currently about fifty permanent physicists, of whom about two thirds are researchers from the CEA and one third from the CNRS. The laboratory also hosts a number of associates, postdocs and visitors and about ten young researchers preparing their Ph.D.s. The activity of the laboratory relies on about ten support staff (documentation, computing and administration).