Oleic acid, also known as cis-9-octadecenoic acid, is a naturally occurring fatty acid with the molecular formula C18H34O2 or CH3(CH2)7CH=CH(CH2)7COOH. Its molar weight is 282.46 grams per mole, and its density is 0.9 grams per milliliter. It is an oily liquid with a pale yellow color and a lard-like odor.
Oleic acid is classified as a monounsaturated omega-9 fatty acid. It occurs naturally in animal and vegetal fats. It is part of the human diet, and it is the most abundant constituent of human adipose tissue. It also plays a biological role as an insect pheromone in ants and bees, being released at the time of death in order to trigger the instinct of worker insects to remove the corpse from the hive.