We generalize the van der Waals-Maxwell description of the fluid phase diagram to account for chemical specificities of polar molecular fluids such as hydrogen bonding in water. The theory is based oil the reference interaction site model (RISM) integral equation method in the partially linearized hypernetted chain (PLHNC) approximation. The predictions for the liquid-vapor coexistence of vater are in qualitative agreement with molecular simulations. The theory can be extended to electrolyte as ell as non-electrolyte Solutions, and to ionic liquids.