Brain aging is a multifaceted, multifactorial process involving genetic, environmental, and lifestyle determinants. Cognitive deterioration, the signature of aging, appears as incremental impairments of memory, executive function, and speed of processing, with wide variation in degrees among individuals. This chapter delves into neurobiological processes of brain aging such as synaptic impairment, neuroinflammation, mitochondrial failure, and protein aggregation. It also explores the influence of vascular health, hormonal shift, and oxidative stress on the trajectory of cognition. In addition, we touch on the differentiation between healthy cognitive aging and pathology like Alzheimer’s disease and other dementias. We then review interventions promoting cognitive resilience through neuroplasticity-stimulating interventions, dietary change, exercise, and cognitive training. By incorporating knowledge from neuroscience, epidemiology, and clinical studies, the chapter presents an integrated understanding of brain aging and points toward promising avenues for intervention and healthy cognitive longevity.