The aim of this chapter is to focus on the classification system of periodontal diseases. This chapter covers the need for classification, current classification systems of periodontal diseases, classification of periodontal disease and condition, synopsis of types and characteristics of gingival diseases, and synopsis of types and characteristics of periodontal diseases. Periodontal diseases are classified for the purpose of diagnosis, prognosis and treatment planning, to understand the etiology and pathology of the periodontal diseases, and for logical, systematic separation and organization of knowledge about disease. Classification system should possess a systematic arrangement of groups of disease that have common attributes.