The Simulation Interoperability Standards Organization (SISO) is an international organization dedicated to the promotion of modeling and simulation interoperability and reuse for the benefit of a broad range of M&S communities.

SISO's Conference Committee organizes Simulation Interoperability Workshops (SIWs) in the US and SISO at ITEC in Europe. SISO's Standards Activity Committee develops and supports modeling and simulation standards, both independently and in conjunction with other organizations. SISO is recognized as a Standards Development Organization (SDO) by NATO and as a Standards Sponsor by IEEE. In addition, SISO is a Category C Liaison Organization with ISO/IEC (JTC 1) for the development of standards for the representation and interchange of data regarding Synthetic Environment Data Representation and Interchange Specification (SEDRIS).

The Simulation Interoperability Standards Organization (SISO) originated with a small conference held April 26 and 27, 1989, called, "Interactive Networked Simulation for Training". The original conference attracted approximately 60 people. The group was concerned that there was activity occurring in networked simulation, but that it was occurring in isolation. The group believed that if there were a means to exchange information between companies and groups that the technology would advance more rapidly. The group also believed that once the technology begins to stabilize then there would also be a need for standardization. The technology and the consensus of the community would be captured in the standards as networking or simulation technology matured.

The conferences soon developed into the Distributed Interactive Simulation (DIS) Workshops and were now focused on creating standards based on the major project SIMNET which was established as the baseline standard from which to move forward. In late 1996, in light of the development of the High Level Architecture (HLA) and with the encouragement of the U.S. Department of Defense Modeling and Simulation Office, the DIS organization transformed itself into a more functional organization called SISO.