A detailed structural determination of the Ni{111}-(root 7x root 7)R19.1 degrees-C6H6 overlayer has been performed using automated fully dynamical low energy electron diffraction I-V analysis. In the most likely geometry (R(p) = 0.26, total energy range : 1552 eV) benzene adsorbs with its center 1.91 Angstrom above an hcp site and with its C-C bonds oriented parallel tothe close-packed rows of the substrate. The molecular radius is found to be slightly expanded relative to the gas phase (1.48 Angstrom and 1.50 Angstrom vs 1.40 Angstrom) and no significant vertical buckling can be seen (< 0.04+/-0.05 Angstrom). The topmost Ni layer is strongly buckled (0.14 Angstrom) with the height of the Ni atoms decreasing with increasing lateral distance from the molecule (+0.08, 0.00, and -0.06 Angstrom with respect to the clean surface). A second similarly low R(p) factor minimum for adsorption on a bridge site was dismissed because of significantly higher R(1) and R(2) values and the extreme molecular distortions of this geometry. The resulting structure is fully consistent with recent UPS and FED studies.