Abiotic stresses associated with climate change, soil degradation, and intensive agricultural practices pose major limitations to crop productivity and food security worldwide. Among emerging technological solutions, nanotechnology has gained increasing attention for its potential to enhance plant performance while reducing environmental inputs and ecological risks. In this chapter, the role of iron oxide-based nanoparticles as functional tools for plant stress alleviation within the framework of sustainable agriculture is comprehensively discussed. The chapter reviews current findings on how iron oxide nanoparticles influence plant growth, photosynthetic efficiency, antioxidant capacity, nutrient homeostasis, and secondary metabolism under major abiotic stresses, including heavy metal toxicity, salinity, drought, alkalinity, and temperature extremes. Both stress-specific effects-such as restriction of toxic ion uptake or mitigation of water-deficit damage-and stress-agnostic mechanisms-such as reinforcement of antioxidant systems and metabolic resilience-are discussed. Particular emphasis is placed on green synthesis approaches, nano–biostimulant integration, and precision application strategies that enhance efficacy while minimizing environmental and phytotoxic risks. Finally, critical challenges related to nanoparticle uptake, translocation, bioavailability, dose dependency, and regulatory considerations are highlighted. Overall, this chapter considers iron oxide nanoparticles not only as advanced nutrient sources but also as multifunctional agents for targeted stress management and sustainable production of crops under increasing environmental constraints.