DuMuX, DUNE for multi-{phase, component, scale, physics, ...} flow and transport in porous media, is a free and open-source simulator for flow and transport processes in porous media. It is based on the Distributed and Unified Numerics Environment DUNE, dune-project.org. Its main intention is to provide a sustainable and consistent framework for the implementation and application of model concepts, constitutive relations, discretizations, and solvers. It has been successfully applied to CO2 storage scenarios, environmental remediation problems, transport of therapeutic agents through biological tissue, and subsurface-atmosphere coupling. DuMuX is part of the OPM (Open Porous Media) initiative, opm-project.org. The development of DuMuX started in January 2007 at the University of Stuttgart.