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Metathesis polymerization is a chain-growth process in which carbon–carbon double bonds of unsaturated monomers are continuously redistributed at a metal–alkylidene (or equivalent) active center, producing a polymer whose backbone unsaturation is a direct consequence of the metathesis event [1]. In organic polymer synthesis the concept is bounded by two principal modes: ring-opening metathesis polymerization of strained cyclic olefins and acyclic diene metathesis polymerization of α,ω-dienes. Essential features are a well-defined metal–alkylidene initiator, typically based on Group VI or Group VIII metals, a (2+2) cycloaddition–cycloreversion sequence that exchanges alkylidene fragments, and retention of an olefin in each newly formed linkage ^[1][2]. Living variants require fast initiation relative to propagation and suppression of chain transfer, so that molecular weight tracks the monomer-to-initiator ratio ^[3]. The process is distinguished from addition polymerization of olefins by the absence of a net change in the degree of unsaturation per repeat unit, and from step-growth condensation by the chain-growth kinetic profile associated with a discrete metal–carbene. Metal-free photochemical variants still operate through an olefin-metathesis elementary step rather than through conventional radical addition ^[4].