Polyunsaturated fat (PUFA) is a type of dietary fat that contains a polyunsaturated fatty acid, which is a subclass of fatty acid characterized by a backbone with two or more carbon–carbon double bonds. PUFAs are considered healthy fats, along with monounsaturated fat. They are found in oils such as canola, olive, rapeseed, corn, sunflower, and soybean oil, as well as in nuts, seeds, and seafood. PUFAs have important dietary functions, and their biosynthesis has received much attention. Plants produce PUFAs from oleic acid, and key enzymes called fatty acid desaturases introduce additional double bonds.

PUFAs are significant components of alkyd resins, which are used in coatings. They have also been studied for their effects on cardiovascular disease, with much attention given to the n-3 PUFAs and their role.

In general, PUFAs are undesirable components of vegetable oils, so there is great interest in their removal from, say, olive oil. One technology for lowering the PUFA content is by selective formation of derivatives with ureas.

To summarize, PUFAs are a type of healthy fat found in oils, nuts, seeds, and seafood. They have important dietary functions and are significant components of alkyd resins. There is also ongoing research into their effects on cardiovascular disease.