Brain tissue is more sensitive to oxidative damage due to many different properties than other tissues. So, the need for protection of brain tissue, which is more prone to oxidative damage than other tissues and organs, is greater than other tissues. Oxidative stress is brought on by a disturbance in the balance between antioxidants and free radicals, which have a scavenging effect on them in biological systems. Increased ROS causes cell damage by causing damage to cell membranes, deterioration in the structure and functions of intracellular proteins, and structural damage to DNA. Oxidative stress is responsible for the pathogenesis of many diseases, especially cancer, diabetes, neurological and cardiovascular diseases, atherosclerosis and inflammatory disorders. Brain tissue is prone to free radical damage because it produces more toxic radicals than other organs. Because the brain has a poorer antioxidant defense system and a higher oxidative metabolism than other organs, it is more vulnerable to ROS-induced damage that can lead to neuronal death. Regional differences in antioxidant system activities and variable metabolic rates in brain tissue may also cause regional accumulation of oxidative damage. In the light of this information, it is aimed to evaluate oxidative stress, the mechanism of oxidative stress formation and the mechanisms of action of oxidative stress on the brain, its effects on intracellular structures and the destruction products formed in oxidative stress with the results of biochemical studies.