Microbial Enhanced Oil Recovery (MEOR) is a cost-effective and eco-friendly technique that exhibits many advantages compared with the other conventional Enhanced Oil Recovery EOR techniques where it does not need huge amounts of energy, like thermal techniques, and it does not depend on the oil price, as much as many chemical techniques. Generally, the cost of a thermal EOR project could be 25$ per barrel of additional oil, and the cost of carbon dioxide and surfactant injection projects could be as high as 30$ and 50$ per barrel of additional oil, respectively. However, the cost of the MEOR process could be 6$ to 10$ per barrel of additional oil, which means it is the cheapest EOR technique to apply since it requires low-cost nutrient brine solutions and slight modifications to the facilities already in place from secondary recovery processes. Therefore, MEOR has great potential to become a viable alternative to the traditional EOR chemical methods. Moreover, MEOR products are all-biodegradable and will not be accumulated in the environment, therefore are environmentally compatible. The effects of bacterial activity within the reservoir are improved by their growth with time, while in EOR technologies the effects of the additives tend to decrease with time and distance from the injection well. This special issue aims to investigate the potential of producing biosurfactants by indigenous bacteria isolated from oil fields, and how to optimize the production of these biosurfactants.