α-Dodecatungstosilicate (α-SiW12O404−) anions form ordered monolayers on Ag(111) and Au(111) surfaces. In-situ STM images reveal that the silicotungstate ion forms a square adlattice with an intermolecule spacing of 10.2 ± 0.5 Å on both Ag and Au surfaces. Additional structures exhibiting either row or rhombic motifs are observed on Au electrodes. The structure of the adlattices can be modeled using a simple model which maximizes the coordination of the silicotungstate ion to the electrode while maintaining van der Waals contacts between terminal oxygens of adjacent silicotungstates.