Cobalt: A parallel, implicit, unstructured Euler/Navier–Stokes solver. Cobalt is a parallel, compressible Euler/Navier-Stokes flow solver applicable to geometries of arbitrary complexity. Its principal design features are stability, accuracy, and ease-of-use. Two- and three-dimensional unstructured grids of arbitrary cell topology are supported along with Overset grids, rigid-body motion, three equations of state, eight turbulence models, and over 20 boundary condition types. Cobalt provides detailed flow field diagnostics and direct output to major commercial post-processors.