Environmental stresses such as drought, salinity, extreme temperature, heavy metals, and pathogen infection significantly limit plant growth and crop productivity worldwide. Nanotechnology has recently emerged as a promising approach to enhance plant tolerance to these stresses. Nanoparticles possess unique physicochemical properties including small size, high surface area, and high reactivity, which allow them to interact efficiently with plant tissues and cellular systems. These materials can improve nutrient uptake, enhance photosynthetic efficiency, regulate hormone balance, and activate antioxidant defense systems that reduce oxidative stress. In addition, nanoparticles can modulate gene expression, influence metabolic pathways, and stimulate the production of protective compounds that enhance plant resilience under stressful conditions. Nanoparticles also play an important role in plant protection by acting as nano-fungicides, nano-bactericides, nano-insecticides, and nano-sensors for disease detection and environmental monitoring. Recent studies demonstrate that different nanoparticles, including metal nanoparticles, metal oxide nanoparticles, and carbon-based nanomaterials, can improve plant performance under both biotic and abiotic stresses. However, concerns remain regarding their toxicity, environmental impact, and long-term sustainability in agricultural systems. This review summarizes recent advances in nanoparticle applications in plant stress management, their molecular and physiological mechanisms of action, and their potential benefits and limitations in sustainable agriculture