Atomic resolution Atomic Force Microscope (AFM)1,2images of the first underpotentially deposited monolayer in the Cu on Au(111) and Ag on Au(111) are presented. These images demonstrate that the structure of this monolayer is very dependent on the nature of the electrolyte in which the upd process occurs. Specifically, Cu exhibits a (&sqrt;3 ×&sqrt;3)‐R30 °C overlayer on Au in sulfuric acid electrolyte, but is incommensurate close‐packed in perchloric acid. Ag shows a 3×3 overlayer in sulfuric acid and a 4×4 overlayer in carbonate and nitrate containing electrolytes. These different structures most likely originate in differing degrees of electrolyte participation in the monolayer.