Emerging evidence has illuminated the critical role of gut microbiota in regulating health and longevity. In this review, we systematically summarize the changes in gut microbiota associated with aging and age-related diseases, including gastrointestinal tract diseases, neurodegenerative disorders, and metabolic dysfunction syndromes. We will also explore the underlying mechanisms, particularly those related to metabolic and immune pathways, highlighting a feedback loop model of "microbial dysbiosis-metabolic dysfunction-chronic inflammation". Furthermore, current interventions related to gut microbiota, including dietary strategies, fecal microbiota transplantation, prebiotics, probiotics, and phage therapies, will be discussed. We will also explore cutting-edge technologies such as artificial intelligence (AI)-driven microbiome analysis, microbial engineering, and organ-on-chip systems, as well as the challenges that remain in this field. Overall, this review provides a theoretical framework and directional guidance for rejuvenating aging and age-related diseases via targeting the gut microbiota.