This paper reports a simple electrodeposition technology that enables rapid production of large-area polymer nanocomposites with layered structures that mimic the nacreous layer of mollusk shells. Uniform, electrostatically stabilized gibbsite nanoplatelets with high aspect ratio are preferentially oriented parallel to the electrode surface when an external direct current electric field is applied. The electroplated ceramic films have uniform thickness, and the thickness can be controlled by adjusting the nanoplatelet concentration of the electroplating baths. Homogeneous, optically transparent nanocomposites are obtained when the interstitials between the aligned nanosheets are infiltrated with polymer. The resulting ceramic−polymer nanocomposites exhibit four-times higher tensile strength and nearly 1 order of magnitude higher modulus than pure polymer films. The covalent linkage between the nanoplatelets and the polymer matrix plays an important role in determining the mechanical properties of these bi...