MOOSE, the Multiphysics Object Oriented Simulation Environment, is a finite-element multiphysics framework largely developed by Idaho National Laboratory. It offers a high level interface to sophisticated nonlinear solver technology, such as BISON for nuclear fuel, Rattlesnake for radiation transport, MAMMOTH for general reactor physics, and more. MOOSE has a straightforward API well suited to how scientists and engineers tackle real-world problems. It is a fully coupled and fully implicit multiphysics solver that is automatically parallel, making it possible to run large simulations and tackle complicated models.