The role of reactive oxygen species (ROS), reactive nitrogen species (RNS), reactive sulfur species (RSS), and selenium are paramount in regulating plant physiology and enhancing resilience against various environmental stressors. ROS are primarily produced in chloroplasts, mitochondria, and peroxisomes as metabolic byproducts, serving as key signaling molecules that fine-tune growth regulation, photosynthesis, and stress responses. The production of ROS necessitates sophisticated antioxidative systems to effectively mitigate oxidative damage and preserve cellular integrity. In this context, RNS, particularly nitric oxide, complements ROS functions by facilitating stress acclimatization and modulating gene expression under adverse conditions. RSS also contributes to cellular signaling pathways, interacting with ROS and RNS to maintain redox homeostasis during stress. Selenium, an essential micronutrient, significantly enhances plant responses to abiotic stresses such as drought and salinity, promoting growth and yield potential. However, excessive selenium can lead to toxicity, causing oxidative stress and physiological damage. The complex interactions among ROS, RNS, RSS, and selenium form a regulatory network that impacts various physiological and pathological processes in plants. In this book chapter, a thorough understanding of these interactions was cumulated which is essential for developing effective agricultural practices and optimizing nutrient management to improve crop productivity and sustainability.