Peri-implantitis is a biofilm-associated inflammatory disease affecting the soft and hard tissues surrounding dental implants, leading to progressive bone loss and potential implant failure. With the increasing global prevalence of dental implant therapy, peri-implantitis has become a significant clinical challenge in modern dentistry. This article reviews current knowledge regarding the pathogenesis, risk factors, diagnostic modalities, and contemporary treatment strategies for peri-implantitis. The role of microbial dysbiosis, host immune response, genetic predisposition, and systemic factors are discussed. Modern therapeutic approaches including mechanical debridement, laser therapy, photodynamic therapy, regenerative surgery, and implant surface decontamination techniques are analyzed. Future perspectives focus on biomarker-based early diagnosis, personalized risk assessment, and bioengineered treatment strategies.