Abstract: The present study examines the magnetohydrodynamic (MHD) stability characteristics of two superposed, electrically conducting viscous fluids saturating a homogeneous porous medium. The fluids are separated by a horizontal interface and subjected to a uniform magnetic field, while Darcy–Brinkman flow resistance arising from the porous structure modifies the momentum transport. By applying linear perturbation theory in conjunction with the normal-mode technique, a generalized dispersion relation is derived that incorporates the effects of magnetic field strength, viscosity stratification, density contrast, and permeability parameters. The analysis reveals that the presence of a porous matrix exerts a strong stabilizing influence by enhancing momentum dissipation and suppressing the growth rate of interfacial disturbances. The magnetic field further augments this stabilization through magnetic tension, particularly for short-wavelength perturbations. The combined action of magnetic damping and porous resistance raises the critical conditions required for the onset of instability, thereby reducing the likelihood of shear-driven or buoyancy-driven interfacial deformation. The results are relevant to geophysical flows, petroleum reservoir engineering, filtration systems, and industrial processes involving magnetized fluid transport through porous structures.