<p>Marine algae-derived neurotoxins, commonly associated with harmful algal blooms (HABs), represent a paradox in marine and biomedical sciences. While traditionally studied for their ecological disruptions and health hazards, these bioactive compounds possess unique biochemical properties with promising therapeutic and technological applications. By summarizing current knowledge and identifying gaps in research, this review systematically examines the biological significance of marine algae, elucidates the mechanisms underlying neurotoxin production, and assesses their biomedical relevance. Furthermore, it explores nanotechnology as a transformative approach for harnessing neurotoxins in drug delivery, biosensing, and theranostics. Particular emphasis is placed on nano-biosensors for precise neurotoxin detection, nanomaterial-based mitigation strategies for HABs, and the use of neurotoxin-loaded nanocarriers in targeted pharmacological interventions. Ethical and environmental considerations surrounding neurotoxin utilization are critically analyzed to ensure sustainable applications. By synthesizing current knowledge and identifying gaps in research, this review hypothesizes that marine algae-derived neurotoxins, when incorporated into nanosystems, can serve as multifunctional agents in precision medicine, neuropharmacology, and diagnostic imaging. Through an interdisciplinary perspective bridging marine biology, toxicology, and nanoscience, this work aims to provide a structured framework for future research, fostering innovation at the intersection of marine biotechnology and nanomedicine.</p>