Oxygen fugacity plays a critical role in planetary evolution, influencing core-mantle differentiation, mantle composition, and surface environments. However, the absence of oxybarometers specifically calibrated for extraterrestrial environments has left the redox conditions of the Moon and other planetary bodies largely unconstrained, hindering our understanding of their formation and evolution. Among the various minerals in mantle-derived magmas, olivine stands out as an ideal recorder of primitive magma conditions, largely immune to post-magmatic processes like fractional crystallization, degassing, and assimilation. The partitioning behavior of vanadium, a multivalent element, between olivine and melt is particularly sensitive to oxygen fugacity, making olivine-based V oxybarometers one of the most reliable tools for redox state estimation. However, existing olivine oxybarometers, while extended to more reducing conditions, remain insufficiently calibrated for the oxygen fugacity and unique melt compositions and temperatures of the lunar mantle. In this study, we recalibrate the olivine V oxybarometer specifically for the Moon by integrating key parameters: the composition of olivine (i.e., forsterite content) from Chang'e-5 samples, crystallization temperatures determined via MAGEMin phase equilibria modeling, and the compositional characteristics of lunar melts. The calibration is conducted across a redox range from ΔIW+3 to ΔIW-2, capturing the oxygen fugacity conditions of the lunar mantle. Using this recalibrated oxybarometer, we compiled and analyzed previously published lunar olivine datasets, enabling a precise determination of the redox state of the lunar mantle. This study provides a critical advancement in understanding the Moon's mantle oxidation conditions, offering new insights into its evolution history and laying the foundation for broader investigations of planetary redox processes.