Organic acids are broadly distributed in nature, and humans have used them in their natural sources since the early ages, essentially for food and drink preparations. Organic acids are low-molecular-weight organic compounds with one or more acidic groups such as carboxyl, sulfonic, alcohol, and thiol groups. These functional groups make organic acids key building block chemicals, which have huge markets, and some of them are still commonly refined from petroleum. Indeed, during the first half of the twentieth century, advances in chemical synthesis offered competitive manufacturing processes. This scenario changed starting from the 1990s with the development of the industrial biotechnology field and the integration of biomass processing industries; fermentation and downstream procedures improved the economics for the biological synthesis. In this chapter, we mainly review the aspects of current or piloting large-scale successful industrial processes for yeast or fungal organic acid productions. Perspectives are also reported.