Chitosan–metal oxide nanocomposite hydrogels have emerged as promising multifunctional materials for biomedical and environmental applications due to their combined biocompatibility, antimicrobial activity, and tuneable physicochemical properties. Native chitosan hydrogels exhibit biodegradability and inherent antibacterial behaviour, yet their limited mechanical strength, structural stability, and moderate antimicrobial efficiency restrict advanced therapeutic use. Incorporation of metal-oxide nanoparticles such as ZnO, TiO₂, CuO, Fe₃O₄, MgO, and CeO₂ significantly enhances mechanical integrity, regulates swelling behaviour, and introduces multiple antibacterial mechanisms including reactive oxygen species generation, membrane disruption, and controlled ion release. This review summarizes recent advances in the design and fabrication of chitosan–metal oxide nanocomposite hydrogels with particular emphasis on microwave-assisted synthesis. Compared with conventional preparation methods, microwave processing enables rapid and uniform heating, controlled nucleation, improved nanoparticle dispersion, and reduced synthesis time, resulting in materials with enhanced reproducibility and performance. The antibacterial mechanisms of both chitosan and metal oxides and their synergistic effects are discussed along with physicochemical characteristics and safety considerations. Furthermore, major applications in wound healing, drug delivery, tissue engineering, dental care, water purification, and antimicrobial coatings are highlighted. Current challenges including nanoparticle aggregation, long-term toxicity, scalability, and regulatory barriers are critically analysed, and future perspectives such as smart responsive hydrogels, AI-guided optimization, and industrial-scale manufacturing are outlined. Overall, microwave-engineered chitosan–metal oxide nanocomposite hydrogels represent a versatile platform for next-generation antimicrobial and regenerative technologies.