Mitochondria, essential organelles known for ATP production and metabolic regulation, play a crucial role in the aging process and the development of age-related diseases. Mitochondrial dysfunction, marked by impaired oxidative phosphorylation, increased reactive oxygen species (ROS), and altered mitochondrial dynamics, is a hallmark of aging. This review comprehensively discusses the mechanisms underlying mitochondrial dysfunction, its impact on cellular senescence, and its contribution to diseases such as neurodegeneration, cancer, cardiovascular disorders, and metabolic syndromes. The paper also highlights emerging therapeutic strategies aimed at restoring mitochondrial health, offering insights into healthy aging and longevity.