Caprylic acid (from the Latin word capra, meaning "goat"), also known under the systematic name octanoic acid is a saturated fatty acid and a carboxylic acid. Its compounds are found naturally in the milk of various mammals, and as a minor constituent of coconut oil and palm kernel oil.

Caprylic acid plays an important role in the body's regulation of energy input and output, a function which is performed by the hormone ghrelin. The sensation of hunger is a signal that the body requires an input of energy in the form of food consumption. Ghrelin stimulates hunger by triggering receptors in the hypothalamus (a small region of the brain responsible for releasing hormones. regulating body temperature and other crucial functions.)

In order to activate these receptors, ghrelin must undergo a process called acylation in which it acquires an -OH group, and caprylic acid provides this by linking at a specific site on ghrelin molecules.