The martian volcano Alba Patera is surrounded by a system of graben which appears to be the result of an extensional stress applied to the region after the construction of the volcano. These faults provide a map of the stress field that created them. We used this information, as well as the recent Goddard spherical harmonic gravity model (GMM-1) and a spherical harmonic representation of the Mars Digital Elevation Model, to constrain models of: (1) the lithospheric flexure under the load of the volcano, (2) the gravitational anomaly due to the volcano, and (3) the magnitude of the extensional stress in the region. We found that elastic lithospheric thicknesses between 10 and 50 km resulted in statistically acceptable fits to the gravity and topography data. We also found that a 1.5-2 kilobar extensional regional stress in conjunction with the axisymmetric stress field of the volcanic load produced a stress field that is consistent with the observed trends of the graben.