Ring-opening metathesis polymerization (ROMP) has grown from an extension of olefin metathesis into a powerful, modular platform for synthesizing precision macromolecules. In this review, we explore the evolution and current landscape of strain-driven ROMP, beginning with historical and mechanistic foundations. A central focus is placed on the concept of ring strain─its theoretical basis, thermodynamic consequences, and practical implications for polymerizability. We critically examine the roles