Oyster Sauce is a viscous dark brown sauce commonly used in Chinese and Filipino cuisine. Oyster sauce is prepared from oysters, brine, umami flavour enhancers such as MSG, and typically contains chemical preservatives to increase its shelf life.

Oyster sauce was invented in 1888 by Mr. Lee Kam Sheung, in Nam Shui Village in Guangdong Province, China. His company, Lee Kum Kee, continues to produce oyster sauce, to this day, along with a wide variety of Asian condiments.

Production
A "true" oyster sauce of good quality should be made by condensing oyster extracts, which is made by cooking oysters in water, where the aqueous mixture is then cooked until a desired viscosity has been reached. No other additives, not even salt, should be added to the sauce since the oysters should provide all the savory flavour. The sauce should be

aromatic with great umami flavour (xīan wèi). Unfortunately this method is expensive and only a handful of manufacturers are willing to use it.

Most oyster sauces are actually diluted solutions thickened with starch, chemical preservatives and caramel, with little or no oyster extracts. In some countries, including the UK, the oyster content in some sauces is lower than its Asian counterparts of the same brand due to laws regulating the import of seafood. Typical oyster sauce also has large amounts of monosodium glutamate added, but in recent years MSG-free varieties can also be found. The taste of MSG and non-MSG variants may not be easily distinguishable.

Vegetarian oyster sauce prepared from mushrooms is also popular and generally cheaper, but contains more taste enhancers.

Use
Oyster sauce is capable of enhancing the flavour of many savory foods. It is often used as a topping for steamed vegetables such as kailan and in stir-fries.