Brain aging is part of the aging of the whole body, largely determining the success of general aging and the quality of life of an older person. Brain aging is a complex multifactorial process that occurs throughout a human’s life, which includes changes at subcellular, tissue, and organ levels as well as at physiological level, mediating changes in neurophysiological (cognitive) functions. The review provides up-to-date data on morphological and physiological changes observed during natural aging; various phenotypes of brain aging are discussed, including both pathologically accelerated and «supernormal» aging; questions of the division between the norm and pathology are raised in the context of changes observed during brain aging; the factors both accelerating and decelerating the aging processes of the brain are considered along with linkage of natural aging with neurodegenerative and cerebrovascular diseases.