Oyster sauce is prepared from oysters, brine, umami flavour enhancers such as MSG, and typically contains preservatives to increase its shelf life.
The sauce was invented in 1888 by Mr. Lee Kam Sheung, in Nam Shui Village in Guangdong Province, China.[1]
His company, Lee Kum Kee, continues to produce oyster sauce, to this day, along with a wide variety of Asian condiments.