Olive oil is widely consumed in Korea, and is a representative fat source in the Mediterranean diet, known to be effective in the prevention of coronary artery disease. In addition, diverse functionalities have been reported, such as anti-cancer, anti-oxidation, and anti-inflammation effects. In this review, the status of production and variety were investigated with respect to the functionalities of olive oil. The main functional constituents of olive oil are oleic acid, known to improve blood cholesterol, and the minor constituents are polyphenol, tocopherol, squalene, and phospholipid, the concentrations of which can be used to distinguish pressed from refined olive oil. A number of studies of the functionality of olive oil have dealt with the minor constituents, and the beneficial functionalities, such as anti-oxidation, anti-inflammation, and improving blood circulation have been reported. This review intensively investigates the functionalities and the responsible components, and suggests that continual studies on olive oil are necessary for the prevention of various metabolic diseases.