Omega-3 fatty acids are actually polyunsaturated fats commonly found in seafood, especially higher fat, cold-water varieties. Examples include sardines, mackerel, herring, trout, anchovy, salmon and tuna. Soybean oil and canola oil also provide some omega-3 fatty acids.

The name Omega-3 is derived from the chemical structure of the fat, in which the third chemical bond at the tail end (omega is the last letter in the Greek alphabet) is unsaturated (position of the first double bond in the hydrocarbon) .