Oenococcus oeni (known as Leuconostoc oeni until 1995) is a Gram-positive bacteria species in the genus of Oenococcus. It used to be the only species in the genus; in 2006, the species Oenococcus kitaharae was identified. As its name implies, Oenococcus oeni holds major importance in the field of oenology, where it is the primary bacteria involved in completing the malolactic fermentation.