Ferrohydrodynamics treats the flow and thermodynamics of magnetically polarizable fluid in response to applied magnetic field. Following its introduction twenty years ago, ferro‐hydrodynamics has developed as a branch of mechanics similar to magnetohydrodynamics and electrohydrodynamics. Unique phenomena of ferrofluids and related media are manifested in hydrostatics, inviscid and viscous flows, magnetically induced flow instability, magnetic stabilization of flow, generation of antisymmetric stress, and magnetic multiphase flow. Certain of the phenomena serve as bases of developed technology in seals, dampers, accelerometers, and cooling techniques with new applications under active development in tribology, acoustics, printing, instrumentation, and other areas. Ferrohydrodynamic principles underlie also the development of magnetic multiphase systems yielding turbulence prevention of moving‐bed operations in the process industry. Major concepts and advances of the field are presented in the context of the continuum mechanical framework.