This review provides an extensive overview of stimulus-responsive hydrogels, highlighting their theoretical foundations, modern advances, and applications in healthcare and industry. Hydrogels, characterized by their high hydrophilicity and biocompatibility, have become versatile materials with applications in drug delivery, tissue engineering, and implants. The review discusses various response modalities, including temperature, pH, chemical, light, electric, and shear-sensitive hydrogels, detailing the mechanisms and theoretical analyses behind these responses. It also explores the mechanical behavior and solute transport properties of hydrogels, emphasizing the importance of understanding these aspects for effective biomedical applications. The section on pH-responsive hydrogels delves into the polymer composition, swelling behavior, and controlled drug delivery applications, providing specific examples such as the use of anionic hydrogel networks for oral protein delivery. The review concludes by discussing the potential of pH-responsive hydrogels in targeted drug delivery and their role in improving healthcare outcomes.This review provides an extensive overview of stimulus-responsive hydrogels, highlighting their theoretical foundations, modern advances, and applications in healthcare and industry. Hydrogels, characterized by their high hydrophilicity and biocompatibility, have become versatile materials with applications in drug delivery, tissue engineering, and implants. The review discusses various response modalities, including temperature, pH, chemical, light, electric, and shear-sensitive hydrogels, detailing the mechanisms and theoretical analyses behind these responses. It also explores the mechanical behavior and solute transport properties of hydrogels, emphasizing the importance of understanding these aspects for effective biomedical applications. The section on pH-responsive hydrogels delves into the polymer composition, swelling behavior, and controlled drug delivery applications, providing specific examples such as the use of anionic hydrogel networks for oral protein delivery. The review concludes by discussing the potential of pH-responsive hydrogels in targeted drug delivery and their role in improving healthcare outcomes.