Microalgae are seen as the most promising flexible feedstock, being considered the crop of the future. They grow fast, just needing sunlight, carbon dioxide and minerals. They contain high value ingredients, such as proteins, carbohydrates, lipids, nucleic acids and others (carotenoids and polymers). Thus, they can be produced for a wide range of markets, including human and animal nutrition, cosmetics, pharmaceuticals and biofuels. However, the production cost is still high, limiting their commercial applications to high-valued compounds. The reduction of these costs can be obtained with efficient bioreactor designs, which are able to achieve high areal biomass productivities. In this context, Computational Fluid Dynamics (CFD) may play an important role in the optimization of bioreactor design, analysing the interaction of hydrodynamics, light supply, heat and mass transfer and biological kinetics. This study addresses the recent advances in CFD modelling of both open pond and closed bioreactors.