Alzheimer’s disease is a progressive neurodegenerative disorder characterized by cognitive decline and neuropathological hallmarks such as amyloid beta plaques and neurofibrillary tangles. In recent years, chronic infections have been proposed as potential contributors to Alzheimer’s disease pathogenesis. Periodontitis, a common chronic inflammatory condition, is predominantly associated with Porphyromonas gingivalis, a gram-negative anaerobic bacterium. Emerging evidence suggests that P. gingivalis may influence Alzheimer’s disease development through systemic inflammation, blood brain barrier disruption, and direct neurotoxic effects of its virulence factors. This review summarizes current evidence from experimental and clinical studies linking P. gingivalis with Alzheimer’s disease and discusses possible mechanisms and implications for future research.