Periodontitis is a chronic inflammatory disease affecting the tooth-supporting structures, and its closely linked to diabetes mellitus through a well-established bidirectional relationship. Diabetes exacerbates periodontal destruction via systemic inflammation, oxidative stress, and immune dysfunction, while periodontitis can impair glycemic control by increasing systemic inflammatory burden. The pathogenesis of periodontitis remains only partially understood, involving microbial dysbiosis, host immune responses, and metabolic disturbances. The 2018 classification system defines stages and grades based on disease severity and progression risk. Epidemiological data reveal a high global prevalence, particularly among individuals with type 2 diabetes. Studies have shown that periodontal therapy contributes to improved glycemic control and may reduce cardiovascular risk. Despite its clinical significance, periodontitis remains underdiagnosed in the context of diabetic care. Effective management requires integrated medical and dental collaboration, targeting both glycemic regulation and periodontal health. This dual approach offers mutual benefits for reducing complications and improving long-term outcomes in diabetic patients. In this review, we present the current knowledge on the relationship between diabetes and periodontitis, focusing on epidemiology, pathogenesis, and management.