Oxidative stress is a key factor in neurodegenerative diseases, including Alzheimer's and Parkinson's. It arises from an imbalance in the redox state of cells, often due to excessive reactive oxygen species (ROS) or dysfunction of antioxidant systems. ROS can damage cells by oxidizing proteins, DNA, and lipids, leading to neuronal dysfunction and death. While oxidative stress is implicated in various neurodegenerative diseases, antioxidant therapies have not been effective in clinical trials. This review discusses the sources of ROS in neurodegenerative diseases, the mechanisms of oxidative stress, and the failure of antioxidant treatments. Mitochondrial dysfunction is a major contributor to ROS production, with mitochondrial dysfunction leading to increased ROS and oxidative stress. NADPH oxidase and xanthine oxidase are also involved in ROS production. Despite the role of oxidative stress in disease pathogenesis, antioxidant therapies have not shown significant clinical benefits. The review highlights the complexity of oxidative stress in neurodegeneration and the need for targeted therapies to reduce oxidative stress and slow disease progression.Oxidative stress is a key factor in neurodegenerative diseases, including Alzheimer's and Parkinson's. It arises from an imbalance in the redox state of cells, often due to excessive reactive oxygen species (ROS) or dysfunction of antioxidant systems. ROS can damage cells by oxidizing proteins, DNA, and lipids, leading to neuronal dysfunction and death. While oxidative stress is implicated in various neurodegenerative diseases, antioxidant therapies have not been effective in clinical trials. This review discusses the sources of ROS in neurodegenerative diseases, the mechanisms of oxidative stress, and the failure of antioxidant treatments. Mitochondrial dysfunction is a major contributor to ROS production, with mitochondrial dysfunction leading to increased ROS and oxidative stress. NADPH oxidase and xanthine oxidase are also involved in ROS production. Despite the role of oxidative stress in disease pathogenesis, antioxidant therapies have not shown significant clinical benefits. The review highlights the complexity of oxidative stress in neurodegeneration and the need for targeted therapies to reduce oxidative stress and slow disease progression.