Turmoil of petroleum oil prices, energy, and environmental security, and its finite sources has made biodiesel a more attractive renewable fuel. Biodiesel, a mixture of fatty acid methyl esters (FAMEs) is conventionally derived from either vegetable oils or animal fats. However, using these conventional sources has raised food security concerns and their succinct supply can serve only for a small fraction of existing demand for transport fuels. Furthermore, the cost and acreages needed for the production of vegetable oils has impeded its use as a feedstock and necessitated to look for an alternative feedstock. Recently, much emphasis has been laid on oleaginous microorganisms for their ability to synthesize lipids under stress conditions. In comparison to vegetable oils, microbial oils have many dividends, such as short life cycle, less industrious, less land requirement, independent of season and climate, and easier to scale-up. This chapter attempts to focus light on recent research on oleaginous yeast, mold, bacteria, and microalgae as prospective oil resources for biodiesel production in the near future. In addition, the biochemistry of lipid accumulation, lipid enhancement via biochemical, metabolic and transcription factor engineering approaches, and fermentation processes have been discussed. © Springer Nature India Private Limited 2020.