Abstract: Terpenoids, as key secondary metabolites in Inonotus hispidus, possess significant medicinal value. However, their natural biosynthetic efficiency remains relatively low. The application of exogenous inducers was demonstrated to significantly enhance terpenoid production in this fungus. To elucidate the regulatory role and molecular mechanisms of exogenous oleic acid on triterpene metabolism, Inonotus hispidus was treated with 3% oleic acid, and its effects on mycelial growth, triterpene accumulation, and gene expression were systematically analyzed. Through metabolomics profiling, 23 differentially expressed terpenoid metabolites were identified, including seven triterpenoids, five diterpenoids, eight sesquiterpenoids, two monoterpenoids, and one undefined terpenoid. Transcriptomic analysis revealed 35 differentially expressed genes associated with terpenoid biosynthesis, consisting of one squalene oxygenase gene, nine terpene synthase (TPS) genes, and 25 cytochrome P450 (CYP450) genes. Further q-PCR validation confirmed that the expression of TPS-6618 was significantly upregulated by oleic acid, whereas the expression of CYP450-7867 was inhibited. This study elucidates the regulatory mechanism of oleic acid on terpenoid biosynthesis in Inonotus hispidus at both metabolic and gene expression levels, providing a theoretical foundation for understanding the molecular mechanisms of fungal terpenoid synthesis and the breeding of high-yield strains.