<p>Fermented foods and beverages, produced by the intentional growth of microorganisms, have long been among the most widely consumed foods in the human diet. Whether microorganisms are added directly to food substrates, or the growth and activity of autochthonous microorganisms colonizing food substrates is encouraged by selective conditions, the production of organic acids, ethanol and other metabolic end products enhance the safety, shelf-life, sensory and functional properties of foods. Whereas some fermented foods may be produced by communities dominated by only a few taxa of limited phylogenetic diversity, others are produced through the concerted action of diverse microbial communities. In this Review, we describe the ecological interactions shaping microbial community structure and function across various categories of fermented foods by providing specific examples. We also describe how the manufacture, quality and sustainability of even traditional fermented foods can be improved by contemporary technologies. Finally, we briefly discuss current research on the ecological impact of microorganisms found in fermented food on the human gut.</p>