CYP2C9 also known as Cytochrome P450 2C9 is a member of the cytochrome P450 superfamily of enzymes that catalyzes oxidative metabolism of diverse xenobiotics and endogenous lipids, contributing to hepatic drug clearance and bioactivation pathways. The enzyme functions in the endoplasmic reticulum as part of the P450 electron transfer chain and intersects with redox homeostasis, lipid signaling, and detoxification networks. Interindividual variation in CYP2C9 expression and activity is a key determinant of metabolic capacity and influences susceptibility to adverse drug responses and drug–drug interactions.