Cooking oil is purified fat of plant or animal origin, which is liquid at room temperature. Common plant-derived cooking oils (vegetable oils) are derived from nuts, seeds, grains and beans. Most animal fats are solid at room temperature (and thus not considered oils), but fish, whales and some other cold-climate animals have oils.

Cooking oil is most often used to fry or deep-fry food, or to preserve it.

Oil can be flavoured by immersing aromatic food stuffs such as fresh herbs, peppers and so forth in the oil for an extended period of time. However, care must be taken when using garlic and onions to prevent the growth of botulism in this medium.

Some of the many different kinds of vegetable oils are; grape seed oil, safflower oil, sunflower oil, olive oil, canola oil, peanut oil, cashew oil and sesame oil.