This article presents a novel method for the de novo synthesis of circular olefin copolymers, specifically ethylene/α-olefin copolymers, using industrial feedstocks such as ethylene and α-olefins. The authors describe a process that involves coordination copolymerization of ethylene and α-olefins with a designed functionalized chain-transfer agent, followed by modular assembly of the resulting AB telechelic polyolefin building blocks through polycondensation. This approach allows for the production of a series of ester-linked PE-based copolymers, including linear low-density polyethylene (LLDPE), polyolefin elastomers (POE), and olefin block copolymers (OBC). These materials not only retain the thermomechanical properties of conventional PE-based materials but also exhibit full chemical circularity via simple transesterification and enhanced adhesion to polar surfaces. The closed-loop recycling of these materials is demonstrated through efficient depolymerization and repolymerization processes, achieving quantitative interconversions between telechelic building blocks and high-molecular-weight ester-linked polyolefins. The study highlights the potential of this method for the sustainable production and recycling of circular olefin copolymers.This article presents a novel method for the de novo synthesis of circular olefin copolymers, specifically ethylene/α-olefin copolymers, using industrial feedstocks such as ethylene and α-olefins. The authors describe a process that involves coordination copolymerization of ethylene and α-olefins with a designed functionalized chain-transfer agent, followed by modular assembly of the resulting AB telechelic polyolefin building blocks through polycondensation. This approach allows for the production of a series of ester-linked PE-based copolymers, including linear low-density polyethylene (LLDPE), polyolefin elastomers (POE), and olefin block copolymers (OBC). These materials not only retain the thermomechanical properties of conventional PE-based materials but also exhibit full chemical circularity via simple transesterification and enhanced adhesion to polar surfaces. The closed-loop recycling of these materials is demonstrated through efficient depolymerization and repolymerization processes, achieving quantitative interconversions between telechelic building blocks and high-molecular-weight ester-linked polyolefins. The study highlights the potential of this method for the sustainable production and recycling of circular olefin copolymers.