Plastics, structural polymers made from monomers, are ubiquitous in modern life and have unique benefits. To prevent accumulation in the environment or incineration at their end of life, they must however be reused or recycled in ways not yet implemented today. In many cases, the polymerization process can be efficiently reversed in depolymerization recycling, and monomers regained and purified, providing the basis for materials at the same quality level as in the previous life cycle but at moderate energy intensity and better carbon footprint. As such, depolymerization is very likely the key enabler for some classes of polymers, especially in applications where they are intrinsically mixed with other materials or crosslinked. This book reviews the fundamental polymer science briefly, introduces the respective processing technologies and life cycle considerations. Specific examples from different plastics applications including automotive, construction and textiles help to analyze how depolymerization positions itself in the hierarchy of recycling approaches and its contributions to a circular value chain transformation, including design for recycling. This compact overview will help a reader understand and approach depolymerization recycling in the necessary context of scale, sustainability and value chain thinking.