Currently citric acid is the most produced organic acid in the world. The economic potential, biochemistry, choices of microorganism employed, raw materials, types of fermentation, factors affecting citric acid production, quantification techniques and recovery techniques are discussed. Global production is expected to increase further with increasing demand. Microbial strains which are capable of fermenting any substrates have been developed to maximize the utilization of industrial waste water, agro-industrial waste and provide a more efficient and environmentally friendly production process.