By adding an orientational free-energy term based on Maier-Saupe theory to the statistical associating fluid theory(SAFT) equation, we have developed a versatile equation of state for describing the phase behavior of carbonaceous pitches, a polydisperse class of discotic nematic liquid-crystalline materials that exhibits both thermotropic and lyotropic behavior. SAFT-liquid crystal (SAFT-LC) can be used to describe the phase behavior of carbonaceous pitches both at conditions where orientational effects are relatively minor (i.e., isotropic liquid-liquid equilibria in the presence of solvent) and at conditions where such effects dominate (e.g., the effect of pitch composition on the isotropic/nematic phase transition). SAFT-LC contains five well-behaved, adjustable parameters: three in SAFT for defining the binary interaction parameters and two in LC for describing the clearing temperature of a pitch pseudocomponent. Predictions of SAFT-LC for phase densities, product yields, and mesophase percentages obtained via a supercritical extraction process for producing mesophase pitch were found to be in reasonable agreement with experiment. In addition, the experimentally observed ability of high molecular weight, 100% mesophase pitches to dissolve up to 20 wt % toluene without phase separation was predicted.