Microalgae are the photosynthetic single-celled microorganism with a microscopic diameter of only 3-8 microns. It has survived over 2.5 billion years due to its unique outer cell wall. The self-rejuvenation and rapid growth (4 new cells every 17 to 20 hours) helps to produce lipids, proteins and carbohydrates in large amounts over a short period of time by using CO2, sun light, sugar, N2, P, K as nutrient. These characteristics have drawn the attention of scientist and engineers for possible production of green energy. This study reviews the available species in literatures, their oil content, lipid content and lipid productivity per day as a prospective biodiesel source. Microalgae production techniques, harvesting, oil extraction, conversion technologies underpinning biodiesel production are also outlined. The review shows that microalgae biodiesel blends B20 produces engine performance closer to that of petroleum diesel, and it reduce engine emission compared to diesel. It can be concluded that the algae biodiesel/green diesel has the potential to become an alternative source of biodiesel to meet the increasing world energy demand