A three-dimensional gravity modeling combined with integrated heat flow and elevation modeling is conducted to map out the crustal and lithospheric mantle thickness in the Alboran Basin, in the westernmost Mediterranean. A ``sediment''-corrected Bouguer anomaly has been derived using a depth-to-the-basement map and densities determined from well logs and seismic data. The gravity effect of the base of the lithosphere has been removed from the sediment-corrected Bouguer anomaly to obtain a ``crustal'' Bouguer anomaly, which has been inverted for crustal thickness. The resulting lithospheric structure is further constrained by elevation data under the assumption of local isostasy. The low residual elevation anomalies obtained (+/-100 m in average) suggest that the area is in local isostasy, particularly the medium- and long-wavelength topography features. Variations in crustal thickness range from 36 km underneath the Betic and Rif Chains to