<p>Biopolymer-based hydrogels have emerged as versatile platforms for water purification due to their tunable structure, high hydrophilicity, and environmental compatibility. In this comprehensive review, we evaluate recent progress in the development and application of cellulose-, starch-, and chitosan-derived hydrogels for the adsorption of heavy metal ions from contaminated water. Emphasis is placed on the synthesis strategies, structural modifications, physicochemical characteristics, and functional group interactions that enhance adsorption capacity and selectivity. The role of crosslinking methods, polymer blends, and composite formulations is critically examined in relation to their mechanical integrity and regeneration potential. Moreover, we discuss adsorption isotherms, kinetic models, and thermodynamic behavior reported in the literature to highlight structure–function relationships. Challenges related to stability, reusability, and scale-up are also identified, along with emerging approaches such as stimuli-responsive hydrogels and nanocomposite designs. This review underscores the significance of macromolecular engineering in tailoring biohydrogels for sustainable and efficient removal of toxic metal ions, offering guidance for future development in water remediation technologies.</p> Graphical abstract <p></p>