Tropospheric ozone (O3) pollution is a significant threat to plant health, leading to oxidative stress, reduced photosynthesis, and decreased crop yields. This chapter examines melatonin (N-acetyl-5-methoxytryptamine) as a powerful phytoprotective agent against ozone-induced damage. Melatonin functions both as a direct scavenger of reactive oxygen species (ROS) and as a regulator of antioxidant defense mechanisms. It enhances enzymatic antioxidants like superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), as well as non-enzymatic antioxidants such as ascorbate and glutathione, helping plants manage oxidative stress caused by ozone exposure. Additionally, melatonin plays a key role in regulating stress-responsive gene expression, promoting the activation of protective genes, and delaying senescence. By maintaining photosynthetic efficiency and suppressing ethylene biosynthesis, melatonin helps prolong plant vitality under stress conditions. These effects are particularly important in crops and horticultural species, where ozone exposure can lead to significant reductions in yield and quality. Case studies demonstrate the dose-dependent efficacy of melatonin in mitigating ozone stress across different plant species, showing its potential to reduce oxidative damage and enhance growth under ozone pollution. However, challenges remain in applying melatonin, such as the species-specific responses observed and the need for careful optimization of application methods. This chapter also explores practical applications, including foliar sprays and genetic engineering to boost melatonin production in plants. While promising, these methods require further research to ensure their effectiveness and ecological safety. In conclusion, melatonin holds great promise as a tool to enhance plant resilience against rising ozone levels, supporting agricultural productivity and food security in a changing climate.