Oxidative stability is the extent to which a substance, typically a fat, oil, or fat-containing food, can withstand the stress of oxidation before rancidity develops. It depends on fatty acid composition, with saturated and monounsaturated fats resisting better than polyunsaturates, and on the presence of natural or added antioxidants such as tocopherols. Laboratories quantify it with accelerated tests like the Rancimat or Oxidative Stability Index, which heat the oil under airflow and measure the induction time before volatile acids appear. High oxidative stability predicts long frying life and shelf life, guiding the selection of oils for snacks, bakery, and foodservice, and the dosing of antioxidants where regulations permit.