Abstract <p>Seaweed extracts have emerged as potential biostimulants that promote plant growth and enhance tolerance to biotic and abiotic stresses across a broad range of crops, attributed to their rich and diverse biomolecular composition. Abiotic stresses represent a substantial threat to global agricultural productivity. The extensive diversity of seaweed species and the variability in extraction methodologies underscore the need for comprehensive studies to elucidate how these extracts confer stress tolerance in crops. Under drought stress, seaweed extracts enhance key physiological processes, including stomatal regulation, osmotic adjustment, photosynthetic efficiency, and the accumulation of soluble sugars. They also mitigate the detrimental effects of reactive oxygen species (ROS) by increasing antioxidant activity and modulating hormonal pathways, particularly abscisic acid (ABA) signaling. In salinity stress, seaweed extracts alleviate stress by reducing the Na⁺/K⁺ ratio and preserving membrane integrity. Further, seaweed extracts play a critical role in mitigating temperature-related stresses, such as heat and cold stress, through the activation of heat shock proteins (HSPs), late embryogenesis abundant (LEA) proteins, and other stress-responsive proteins. The synergistic effects of seaweed biomolecules effectively counteract oxidative damage and maintain membrane stability under various stress conditions. In addition to enhancing tolerance to abiotic stresses, seaweed function has been implicated in sustaining the photosynthetic performance of plants through delayed senescence, further supporting their utility in improving crop resilience and productivity.</p>