Mitochondrial dysfunction is a key factor in brain aging and age-related diseases. Mitochondria, essential for energy production, calcium regulation, and apoptosis, are involved in numerous cellular processes. As mitochondria decline with age, they contribute to various diseases, including cancer, diabetes, and neurodegenerative disorders. The Mitochondrial Theory of Aging, which posits that mitochondrial dysfunction drives aging, is a central concept in understanding these processes. Mitochondrial dysfunction leads to increased ROS production, oxidative stress, and impaired cellular functions, contributing to inflammation, cognitive decline, and neurodegenerative diseases such as Huntington's, Parkinson's, and Alzheimer's. The review discusses the structure and function of mitochondria, the causes and consequences of mitochondrial dysfunction in aging, and current therapies to mitigate its effects. It highlights the role of mitochondrial dysfunction in brain aging, emphasizing its impact on cellular homeostasis and the progression of neurodegenerative diseases. The review also explores the mechanisms of mitochondrial dysfunction, including the accumulation of mtDNA mutations, impaired mitochondrial biogenesis, and disrupted mitochondrial dynamics, which contribute to aging and disease. The study underscores the importance of understanding mitochondrial dysfunction to develop effective interventions for aging and age-related diseases.Mitochondrial dysfunction is a key factor in brain aging and age-related diseases. Mitochondria, essential for energy production, calcium regulation, and apoptosis, are involved in numerous cellular processes. As mitochondria decline with age, they contribute to various diseases, including cancer, diabetes, and neurodegenerative disorders. The Mitochondrial Theory of Aging, which posits that mitochondrial dysfunction drives aging, is a central concept in understanding these processes. Mitochondrial dysfunction leads to increased ROS production, oxidative stress, and impaired cellular functions, contributing to inflammation, cognitive decline, and neurodegenerative diseases such as Huntington's, Parkinson's, and Alzheimer's. The review discusses the structure and function of mitochondria, the causes and consequences of mitochondrial dysfunction in aging, and current therapies to mitigate its effects. It highlights the role of mitochondrial dysfunction in brain aging, emphasizing its impact on cellular homeostasis and the progression of neurodegenerative diseases. The review also explores the mechanisms of mitochondrial dysfunction, including the accumulation of mtDNA mutations, impaired mitochondrial biogenesis, and disrupted mitochondrial dynamics, which contribute to aging and disease. The study underscores the importance of understanding mitochondrial dysfunction to develop effective interventions for aging and age-related diseases.