The release of molecular strain has long been harnessed as a powerful driving force in chemical synthesis. A fundamental concept in organic chemistry is 'ring strain', which is used to explain the heightened reactivity of three-membered rings due to deviations from ideal bond angles. Consequently, 'strain release' has been widely employed in organic synthesis as a powerful tactic to increase reaction rates, finding applications in total synthesis, polymer science, bioconjugation bioisosterism; it is also an important concept in biosynthesis (Figure ). However, despite the common belief that such pent-up strain energy fully explains the reactivity of species such as small rings, cycloalkynes and cyclo-(E)-alkenes, even the simplest of these systems presents a paradox: cyclopropanes display markedly heightened ring-opening reactivity compared to cyclobutanes (krel(cyclopropane) = 10 4 -10 7 for intramolecular ring-opening reactions), despite having nearly identical strain energies (27.5 and 26.5 kcal mol -1 respectively). This puzzle has been the subject of extensive theoretical investigations. Stirling et al. proposed that cyclopropane relieves a larger proportion of angle strain (~75%) than cyclobutane (~50%) upon ring-opening, while the groups of Hoz and Houk argued that differences in electronic structure (i.e., bonding) are instead the cause of the reactivity difference. Hoz proposed Figure . Ring strain in organic chemistry. a Examples of strain release driven reactivity, including total synthesis, bioconjugation reactions, ring-opening polymerization, and bioisostere synthesis. b Ground state models for electron delocalization in three-membered rings. c This work: Strain release and delocalization combine to enhance reactivity through lower activation barriers and earlier transition states.