Short-Lived Radionuclides (SLRs) with million-year lifetimes serve as chronometers of Early Solar System (ESS) formation and can reveal active nucleosynthesis in our Galaxy. Among the nuclides whose decay signatures are preserved in meteorites, the extinct radionuclide 92 Nb is one of the few confirmed proton-rich SLRs, and the ESS 92 Nb/ 92 Mo abundance ratio serves as a sensitive probe of proton-rich nucleosynthesis. However, the interpretation of this ratio is complicated by uncertainties in both nuclear reaction rates and the astrophysical environments. Because 92 Nb is shielded by the stable isobars 92 Zr and 92 Mo, it cannot be produced through β-decay chains. Instead, it must be synthesized through direct reactions in explosive supernova environments, where the photoneutron reaction on 92 Nb is a key regulator and currently dominates the uncertainty in the nuclear reaction networks producing 92 Nb. Direct measurements of this reaction are presently not feasible. Therefore, recommended values have relied on theoretical calculations. Here, we present the first experimental constraint on this reaction. This newly constrained reaction rate significantly increases the predicted 92 Nb abundance in relevant supernova environments, thereby shifting model predictions in the direction needed to ease the long-standing discrepancy in the ESS 92 Nb/ 92 Mo ratio by removing one of the dominant nuclear uncertainties in the 92 Nb production network.