Marine microalgae represent a versatile and sustainable resource for biotechnology owing to their rapid growth, high metabolic plasticity, and ability to synthesize diverse bioactive compounds. This review examines the state-of-the-art in the biotechnological applications of marine microalgae, focusing on three major arenas: (1) biofuel and energy production, (2) high-value bioproducts for food, nutraceutical, pharmaceutical and cosmetic uses, and (3) environmental applications including bioremediation and waste-to-worth valorization. The cultivation strategies, strain improvement, downstream processing, techno-economic and life-cycle considerations, and regulatory and commercial challenges. Emerging trends such as synthetic biology, co-cultivation systems, integrated biorefineries, and circular economy models are highlighted. Finally, the present perspectives on how marine microalgae can contribute to global sustainability goals and identify important future research directions for unlocking their full potential.
