<p>The controlled synthesis of zinc oxide ceramics with tailored morphology and crystallinity remains central in advancing its functional applications. The use of protein-based eggshell membrane as a template for synthesizing zinc oxide resulted in the formation of single-crystal platelets and polyhedrons. The eggshell membrane as a template is capable of providing active sites for ion coordination and nucleation. Structural and morphological analysis confirmed the evolution of an assembly of nanocrystallites anchored on a fibrous network replicating the interwoven structure of eggshell membrane into single-crystal platelets and polyhedrons at relatively higher calcination temperatures. Transmission electron microscopy investigations revealed the coalescence of primary nanocrystallites into larger single-crystal domains and the presence of coherent lattice junctions across the attachment interfaces, indicating oriented attachment growth, a non-classical crystal growth process, as a plausible mechanism for the growth of ZnO single crystals. The protein-rich eggshell membrane contains functional groups that can interact with inorganic precursors, providing nanoscale confinement that promotes aggregated growth of crystallites favourable for oriented attachment. The results of this study offer insights into crystal engineering through bio-templating and also demonstrate the utility of eggshell membrane as a platform for the green and sustainable synthesis of metal oxides.</p> Graphical abstract <p></p>