This book explores the scientific development in the field of algal-based nanomaterials synthesis, production methods, and commercial and utilization aspects of phyconanomaterials to address a range of problems of humanity. Nanomaterials have been recently explored for and employed in environmental remediation, biomedical applications, agriculture, food industries, energy sectors, cosmetics, biolabeling, and space due to their versatility and wide range of applicability owing to their peculiar material characteristics and other attributes. Their conventional synthesis approaches are replacing green methods as the latter is comparatively economical, energy-efficient, and eco-friendly. Biological entities and derived materials-based nanomaterials synthesis is such a green approach. Using natural systems to synthesize nanomaterials does not leave behind any toxic compounds generally produced as by-products when physical or chemical methods are employed. Phyconanotechnology, a green way of synthesizing nanomaterials, can be used to overcome this issue. In the proposed book, algal diversity-based nanomaterials synthesis and their applications will be presented to the readers.