SPYTHIA is an event level Monte Carlo program which simulates particle production and decay at lepton and hadron colliders in the Minimal Supersymmetric Standard Model (MSSM). It is an extension of PYTHIA 5.7, with all of its previous capabilities. This paper is meant to supplement the PYTHIA/JETSET user manual, providing a description of the new particle spectrum, hard scattering processes, and decay modes. Several examples of using the program are provided.