OpenMM is a toolkit for molecular simulation. It can be used either as a stand-alone application for running simulations, or as a library you call from your own code. It provides a combination of extreme flexibility (through custom forces and integrators), openness, and high performance (especially on recent GPUs) that make it truly unique among simulation codes.

OpenMM is developed at Simbios, a National Center for Biomedical Computing that researches and develops software for physics-based simulations of biological structures. Funded by the National Institutes of Health, Simbios is based at Stanford University and has a network of collaborators throughout the world.