The exponential growth of plastic production and the persistence of plastic waste in the environment have created a global pollution crisis. Currently, only 9% of plastic waste is recycled, predominantly through mechanical recycling that produces lower-quality materials. This review examines chemical recycling technologies that convert plastic waste back into monomers or valuable chemicals, enabling true circularity. Polyolefins (polyethylene, polypropylene), polyesters (PET), and mixed plastics are discussed. Recent advances in pyrolysis, solvolysis, and catalytic depolymerization are highlighted, along with upcycling strategies that transform waste plastics into higher-value products such as carbon nanotubes, lubricants, and surfactants. Industrial case studies and remaining challenges including feedstock heterogeneity, catalyst deactivation, and economic viability are addressed.