Octyl gallate, designated E311 in the European additive numbering system, is an antioxidant used to protect fats and oils from oxidative rancidity. It belongs to the gallate family, esters of gallic acid, alongside propyl gallate (E310) and dodecyl gallate (E312), and it works by scavenging the free radicals that propagate lipid oxidation chains. Typical applications include edible fats, margarines, processed meats, and snack products where shelf life depends on keeping unsaturated fats stable. Because gallates can be lost during high-temperature processing and have shown some allergenic potential in sensitive individuals, usage levels are regulated and the additive must be declared on labels. Modern clean-label trends have pushed many manufacturers toward tocopherols and rosemary extract as alternatives, but octyl gallate remains an authorised and effective synthetic option.