COPASI[1] (COmplex PAthway SImulator) is an open-source software application for creating and solving mathematical models of biological processes such as metabolic networks, cell-signaling pathways, regulatory networks, infectious diseases, and many others.

COPASI is based on the Gepasi[2] simulation software that was developed in the early 1990s by Pedro Mendes.

The initial development of COPASI was funded by the Virginia Bioinformatics Institute, and the Klaus Tschira Foundation.

Current development efforts are supported by grants from the National Institutes of Health, the BBSRC, and the German Ministry of Education.

The chief software architects are Stefan Hoops and Sven Sahle.