OpenMC is an open source Monte Carlo particle transport code focused on reactor modeling and reactor physics methods research. It is a community-developed code with contributors from many institutions. OpenMC is designed with flexibility and usability in mind. It simplifies the process of simulating complex reactor systems and analyzing their output datasets.

Inputs for OpenMC are generated through a Python API. Using Python rather than traditional text input files allows users to more easily automate the input generation process. The Python API also provides powerful post-processing tools and gives users the ability to quickly analyze their MC data with the many software libraries available in the Python ecosystem.

OpenMC also features a C API (which can be accessed through Python). This API makes it easier to integrate OpenMC into a coupled solver with efficient in-memory data transfers.