Despite the long-standing recognition that ultrahigh molecular weight (UHMW) polymers give rise to chain-length-derived emergent material properties, the synthesis of functional UHMW polymers remains synthetically challenging due to oxygen-mediated radical quenching and chain growth limitations in conventional polymerization methodologies. In this study, we introduce an enzyme-deoxygenated photoiniferter polymerization (Enz-PI) that eliminates oxygen sensitivity from photoiniferter polymerizatio