In a globally aging society, developing an in-depth understanding of cognitive changes, particularly in spatial navigation, is crucial both for healthy aging and in managing neurodegenerative diseases like Alzheimer disease. This chapter reviews current understanding of how cognitive aging and Alzheimer disease affect spatial navigation at the behavioral level and discusses neuronal changes in the brain that contribute to these changes. While an extensive body of behavioral and neuroscientific research offers a detailed understanding of the aging navigational system, our knowledge of how age-related navigational deficits impact everyday navigation and people’s experience of living with declining navigation abilities is surprisingly limited. Similarly, despite the prevalence of spatial disorientation in Alzheimer disease, which leads to an increased risk of getting lost, our understanding of how these deficits progress and their real-world implications is limited. To support independence in aging and improve safety for individuals with Alzheimer disease, future research should focus on real-world everyday navigation, develop targeted interventions, and explore the role of spatial navigation in diagnostics and everyday functioning.