OpenFOAM (Open Field Operation and Manipulation) is primarily a C++ toolbox for the customization and extension of numerical solvers for continuum mechanics problems, including computational fluid dynamics (CFD). It comes with a growing collection of pre-written solvers applicable to a wide range of problems, from complex fluid flows involving chemical reactions, turbulence and heat transfer, to solid dynamics, electromagnetics and the pricing of financial options.

OpenFOAM uses finite volume numerics to solve systems of partial differential equations ascribed on any 3D unstructured mesh of polyhedral cells. The fluid flow solvers are developed within a robust, implicit, pressure-velocity, iterative solution framework. OpenFOAM is produced by OpenCFD Ltd and is freely available and open, not only in terms of source code, but also in its structure and hierarchical design, so that its solvers, utilities and libraries are fully extensible. It is licensed under the GNU General Public License.