Lactobacillus Bulgaricus (LBB) is a bacterium used for the production of yoghurt(yogurt). It is named for Bulgaria, the country where it was first used (it thrives freely on the Balkan Peninsula). The bacterium feeds on milk and produces lactic acid which also helps to preserve the milk. It breaks down lactose and is often helpful to sufferers of lactose intolerance, whose digestive systems lack the enzymes to break down lactose to simpler sugars). One of the biggest importers of the bacterium is Japan.

According to legend, a Bulgarian shepherd in the Balkan Mountains (Stara Planina) who did not have enough vessels to hold all the milk fom his sheep made a bag from a fresh lamb's hide and put the extra milk there. The next morning he found yoghurt in the bag, most likely generated by Lactobacillus Bulgaricus. Other legends suggest that yoghurt was known even to the Bulgars (a nomadic tribe, also known as the proto-Bulgarians), along with kumis, a refreshing, slightly alcoholic drink from mare's milk.

Between 13th and 18th century AD Bulgaria was under the rule of the Ottoman Empire, and Turkish was the official language. The word yoghurt most probably came into English from the Turkish "yogurut".

Although it seems likely that the first yoghurt was made from sheep's milk, nowadays it is made mainly of cow's milk, because the much higher cost of sheep's or goat's milk offsets the higher quality. In most Western countries, commercial production employs various starches, gums, gels, and stabilizers, and uses powdered milk with few or no live bacteria. This practice enables the producers to maximize profits at the expense of consumers, who frequently find raw yoghurt unappealling without the addition of fruits or flavours. It also creates a product far removed in quality from the traditional live bacterial culture.