From a joint analysis of fundamental mode Rayleigh wave group velocities and P-wave receiver functions, we derive a new, high-resolution 3D shear-wave velocity (V_s) model for the crust and uppermost mantle of the Iranian Plateau. The thickest crust (>55km) is located beneath the deforming belts of the Plateau (e.g., the Sanandaj-Sirjan Zone (SSZ) and Talesh-Alborz-Binalud Mountains), whereas regions of lower topography/deformation (e.g., central Iran and the Lut Block), and the regions of very younger deformation such as the Makran Accretionary Wedge and the Zagros Simply Folded Belt (SFB) have a thinner (<45km) crust. Our model reveals a low-V_s tongue-shaped feature, indicating the underthrusting of the Arabian crust beneath central Iran. In the central Zagros, underthrusting of the Arabian crust is steeper, resulting in a narrower (~150km) deforming zone with thicker (~60-65km) crust compared to the crust beneath the broader (~250km) deforming zone and somewhat thinner (~55-60km) crust below the Lorestan Arc. Regions of low-V_s in the upper crust correspond to regions of thick sediments (e.g., the South Caspian Basin, the SFB and foreland basin of the Zagros, and the Makran Subduction Wedge). The subcrustal Rayleigh wave azimuthal anisotropy of the Plateau shows a rather uniform and smoothly-varying pattern. In the NW Zagros the crustal and subcrustal pattern of anisotropy agrees with that previously estimated from the shear-wave core phases, implying that the whole lithosphere deforms coherently, but for other regions (e.g., the western Alborz and Kopet Dag), the anisotropic pattern does not support a coherent deformational fabric throughout the lithosphere.