FOSSIL is our in-house developed simulator of the two-phase non-Newtonian flow of foam through heterogeneous porous media. Combining cutting-edge numerical methods with shared memory parallel computing, FOSSIL provides high-quality simulations of the flow of both compressible and incompressible fluids in a multitude of scenarios including gravity effects and preserving mass conservation. Its intuitive input format allows the user to choose between several mechanistic and population-balance based foam models, various relative permeability and capillary pressure relations, and flexible injection and control criteria.