This chapter provides an overview of the literature on metabolic processes and mechanisms regulating stress-induced leaf senescence. Leaf senescence is a naturally-occurring process during the life cycle of plants but can be induced or accelerated prematurely by environmental stresses. Phytohormones play various roles in regulating plant growth and development, including leaf senescence. Oxidative stress, generated by excessive production of reactive oxygen species (ROS), can accelerate leaf senescence by impacting the integrity of thylakoid membranes within chloroplasts. During leaf senescence, proteins are typically broken down, with a majority of the degradation activity occurring in chloroplasts, adversely affecting photosynthesis. Stress-induced leaf senescence may be mitigated by exogenous application of hormones, growth regulators, and antioxidant compounds. Additionally, the modification of critical genes, such as those involved in pigment or protein synthesis, ROS scavenging, hormone metabolism, and stress responses is another effective approach for developing new plant lines that are able to stay green under adverse conditions.