Microalgae are renowned for their rapid growth, adaptability and their ability to produce a wide variety of bioproducts. Their diverse metabolic capabilities also make them particularly effective in wastewater treatmentWastewater treatment and recovery of valuable products. This chapter presents a comprehensive overview of the significance of microalgae in waste managementWaste management and their integration within circular bioeconomyCircular bioeconomy systems. It begins by exploring cultivation technologies, ranging from open pond to closed bioreactors, and then includes innovative hybrid configurations developed to improve efficiency and scalability. To further enhance treatment performance, the chapter examines the synergistic interactions between microalgae and other microorganisms, as well as the potential for genetic modification. These strategies contribute to more efficient pollutant removal and biomass productivity. The potential for resource recoveryResource recovery is emphasised through applications including biofuelBiofuel production (biogasBiogas, biodiesel biohydrogen), bioplastics, and bioelectrochemical systems. Additionally, microalgae provide a platform for generating high-value bioproducts such as single-cell proteins, pigments and pharmaceutical compounds. The chapter concludes by considering the broader implications of microalgae-based systems for sustainable developmentSustainable development and the transition towards a bio-based economy. These systems align closely with several United Nations Sustainable Development GoalsSustainable Development Goals (SDGs) (SDGs), notably clean water and sanitation (SDG 6), affordable and clean energy (SDG 7) and responsible consumption and production (SDG 12). Although technical and economic barriers continue to limit large-scale implementation, microalgae remain a promising and versatile foundation for integrated wastewater treatmentWastewater treatment and resource recoveryResource recovery.