Most important Essential Fatty Acid is
Essential Fatty Acids (EFA): Are those that cannot be synthesized in human body; they can only be derived from the food
The most important EFA is Linoleic Acid, which serves as a basis for production of other EFA

Dietary sources of EFA:
Linoleic Acid
Linolenic Acid
Arachidonic Acid
Eicosapentanoic Acid