Microalgae Biotechnology: A Sustainable Perspective on the Water–Soil–Air Nexus offers a comprehensive and integrated overview of microalgal biotechnology, emphasizing its role within the interconnected systems of water, soil, and air. The book brings together cutting-edge research and multidisciplinary perspectives to explore how microalgae contribute to sustainable development, addressing global challenges related to environmental management, resource efficiency, and bio-based innovation. The volume covers the full spectrum of microalgal biotechnology, from strain bioprospecting, genetic engineering, and synthetic biology to production systems and technological scalability. It examines microbial interactions in the phycosphere, as well as bioethical and risk considerations associated with environmental release and genome editing. The book highlights advances in high-value compounds such as pigments, lipids, exopolysaccharides, and biopolymers, alongside applications in food, feed, agriculture, and functional ingredients. Environmental applications are strongly represented, including wastewater treatment, bioremediation, carbon capture, and odor control. Emerging frontiers—such as sustainable aviation fuels and space life-support systems—are also explored. Finally, the book provides a robust discussion on sustainability assessment, including metrics, life cycle assessment (LCA), and consumer perception, offering readers both scientific depth and practical insight into the viability of microalgal technologies. This book is designed for researchers, graduate students, and professionals in microalgal biotechnology and related disciplines, including biotechnology, environmental science, food science, and process engineering. It is also a valuable resource for industry stakeholders and decision-makers seeking to better understand the opportunities and challenges associated with microalgae, particularly within the context of the water–energy–food nexus and the growing demand for sustainable technologies.