At present most work treats radiative transport in heterogeneous media as if it were a homogeneous medium, then relies on different methods to simulate the medium heterogeneity or uses similar governing equations with assigned distributions for coefficients. This approach is widely used although almost never found in other fields of heat and mass transport. The lack of generality in present theoretical treatments of radiative transport in heterogeneous media is addressed by rigorous development of a set of governing equations. The new rigorous equations for radiation transport in heterogeneous media are presented for the first time. As part of the development of the new set of equations for electromagnetic and spectral intensity fields, the diffusion approximation is explored.