This review critically assesses the environmental and biotechnological potential of Dunaliella salina, emphasizing how abiotic stress factors shape its physiology, carotenoid and lipid biosynthesis, and its prospects for sustainable applications in industry and ecology. A synthesis of peer-reviewed studies published between 2015 and 2025 highlights the effects of salinity, light intensity, nitrate limitation, temperature, and pH on the species’ metabolic responses, while also comparing cultivation systems such as open ponds and photobioreactors in terms of productivity, efficiency, and scalability. Particular attention is given to advances in omics technologies and genetic engineering that enhance metabolite yields. Results show that high salinity (3–4 M NaCl) and strong light exposure (>300 µmol photons m⁻² s⁻¹) significantly promote β-carotene accumulation, reaching levels of 10–14% of dry biomass, while nitrogen limitation can double lipid content. Photobioreactors demonstrate β-carotene productivities exceeding 600 mg·m⁻²·day⁻¹, outperforming traditional open pond systems. Moreover, D. salina exhibits strong bioremediation capabilities, removing up to 98% of heavy metals in saline effluents and degrading approximately 70% of organophosphate pesticides. Despite these promising results, large-scale industrial deployment remains limited by high production costs, strain variability, and energy requirements for controlled cultivation systems. Nevertheless, the findings position D. salina as a valuable resource for sustainable bioindustries, particularly in the context of circular bioeconomy models and environmental remediation strategies in hypersaline and arid environments. By integrating insights from environmental biotechnology, omics-based optimization, and ecological valorization, this work underscores the strategic importance of D. salina for the development of the green bioeconomy and as a model organism for climate adaptation approaches.