An oyster was a type of mollusk animal native to the planet Earth. Similar creatures could be found on other worlds.

Earth's oysters could be eaten as food and were reputed to an aphrodisiac. When Tasha Yar seduced Data under the influence of polywater intoxication in 2364, she had a meal of Aldebaran wine, oysters, and quetzi ramekins—all aphrodisiacs. When the two later went on a mission to Treva, Data programmed the replicator with these foods, thinking them to be simply foods she liked. (TNG novel: Survivors) The following year, Data repeated the meal when he suggested Aldebaran wine and quetzi ramekins in addition to oysters when he dined with Pris Shenkley. (TNG episode: "Metamorphosis")

Betazed oysters were a similar type of animal and food. (SCE eBook: Wildfire, Book 1)