<p>Cellulose-derived ionic conductors (CICs) are emerging as sustainable alternatives to conventional ion-conducting materials in electrochemical devices. This review highlights recent progress in the synthesis, functionalization, and application of CICs, focusing on cellulose nanofibers (CNF), cellulose nanocrystals (CNC), and bacterial nanocellulose (BNC). Nanocellulose materials offer unique advantages, including high surface area, tunable morphology, mechanical robustness, and environmental compatibility, making them ideal candidates for sensing and energy storage platforms. Ion transport mechanisms in solid and quasi-solid systems are discussed concerning electrostatic interactions, hydration effects, and polymer dynamics. Representative CIC examples are presented in sensors, fuel cells, supercapacitors, and solid-state&#xa0;batteries to showcase performance and versatility. Key challenges, including ionic conductivity limitations, scalability, and testing standardization, are briefly outlined to provide context for future research directions. Overall, this review establishes CICs as a promising material class for next-generation sustainable electrochemical technologies.</p> Graphical abstract <p></p>