Many types of fermented foods, known throughout the world, have been prepared and consumed for centuries for their nutritional value, flavor and stability. This chapter addresses fermented foods commonly known around the world as well as many that are locally produced. It highlights microbiological diversity of these foods. It also addresses the types of foods include dairy products, cereal-based products, fruit and vegetable products, meat products, locally produced traditional fermented foods and innovative functional foods. Lactic acid bacteria play an important role in fermentation of many commonly consumed foods, such as yogurt, cheese, bread, sausage, pickles and olives. Yogurt is one of the most important cultured dairy products consumed throughout the world. Acetic acid bacteria are another important group of bacteria which are essential in vinegar and cocoa fermentations. Yeasts play an important role in the production of bread and many alcoholic beverages, such as beer and wine.