The emergence of high-sulfur content polymeric materials and their diverse applications underscore the need for a comprehensive understanding of the ring-to-chain transformation of elemental sulfur. In this study, we delve into the ultrafast transformation of the elemental sulfur S 8 ring upon photoexcitation employing advanced nonadiabatic dynamics simulations. Our findings reveal that the bond breaking of the S 8 ring occurs within tens of femtoseconds. At the time of bond breaking, most molecules are in the lowest singlet excited state S 1 . S 1 survives for 40−450 fs before relaxing to the quasi-degenerate manifolds formed by the T 1 and S 0 states of the S 8 chain. This suggests that upon photoexcitation the polymerization of the S 8 chains might proceed before the chains relax to their lowest energy states. The derived temporal resolution provides a detailed perspective on the dynamics of S 8 rings upon photoexcitation, shedding light on the intricate processes involved in its excited-state transformations.E lemental sulfur, due to its versatile and intricate nature, is of great interest in many research areas. 1−9 Among the allotropes of elemental sulfur, S 8 stands out as the most stable and prevalent. 10,11 This molecule takes the form of a crownshaped ring (see Figure 1), contributing to a distinct crystal structure with an orthorhombic phase. In the orthorhombic S 8 crystal form, sulfur is characterized by a melting point of ∼113 °C. However, beyond 159 °C, S 8 rings break down into S 8 diradical chains and start to polymerize into long chains. 11