Fish sauce is to Vietnamese cooking what salt is to Western and soy sauce to Chinese cooking. Fish sauce is used as a condiment and flavoring. It is included in practically all recipes.

Raw material of making fish sauce is fish. Only the fresh anchovy fish makes the good quality fish sauce that is clear in color and good smell. Popular throughout Southeast Asia, fish sauce can also be any of various mixtures based on the liquid from salted, fermented fish. This extremely pungent, strong-flavored and salty liquid can range in color from ochre to deep brown. For the pure fish sauce, fresh anchovy fish sauce is selected and mixed with salt by using Vietnamese own traditional process. Fermentation is started once a year, during the fishing season. After about 3 months in the barrel, liquid drips from an open spigot, to be poured back into the top of the barrel. After about 6 months the fish sauce is produced.

The unique characteristic of fish sauce is salty flavor and fishy smell. One interesting characteristic of fish sauce is that it loses its fishy odor once it is mixed in with other ingredients. It is commonly used as seasoning for cooking and dipping seafood and other Vietnamese foods.

The two towns most noted for their fish sauce are Phu Quoc and Phan Thiet. On the label, the "nhi" signifies the highest quality.