Production of microalgal biomass requires large amounts of nitrogen (N) and phosphorus (P). The sustainability and economic viability of microalgae pro- duction could be significantly improved if N and P are not supplied by synthetic fertilizers but with wastewater. Microalgae already play an important role in wastewater treatment, yet several challenges remain to optimally convert waste- water nutrients into microalgal biomass. This book chapter aims to give an over- view of the potential of using wastewater for microalgae production, as well some challenges that should be taken into account. We also review the benefits of combining microalgal biomass production with wastewater treatment.