Stigmastanol, also known as β-sitostanol, is a saturated derivative of β-sitosterol, a common plant sterol (phytosterol). It is a white, crystalline solid with the molecular formula C29H52O. The key structural difference from sitosterol is the saturation of the double bond in the sterol ring system, resulting in a 5α-stanol structure. Its primary and most significant application is in the functional food and nutraceutical industry. As a plant stanol ester, it is clinically proven to lower serum total and low-density lipoprotein (LDL) cholesterol levels by competitively inhibiting the intestinal absorption of dietary and biliary cholesterol. It is a key active ingredient in cholesterol-lowering spreads, dairy products, and dietary supplements. Beyond its direct use as a bioactive ingredient, stigmastanol also finds application as a starting material or reference standard in pharmaceutical and biochemical research. Its saturated structure makes it a stable compound for studying sterol metabolism and for use as a pharmaceutical excipient in certain formulations where the oxidative instability of sterols is a concern.