This chapter details how autoimmunity affects the oral cavity. The oral cavity is a system of hard and soft tissues beginning in the mouth and extending to the oropharynx. It is considered the pathway to the rest of the body, in that initial changes in the health of the oral cavity can have far reaching effects on health. The oral cavity initiates and mediates the intake and output of gasses, fluids, and solids that maintain the human body. Understanding the oral-systemic connection as it presents in autoimmunity is essential for proper treatment and ultimate well-being. This chapter summarizes normal oral anatomy and the oral microbiome, changes that occur due to autoimmunity, and the effects of specific autoimmune diseases and conditions on oral health. Oral healthcare providers are instrumental in identifying and treating the effects of xerostomia, GERD, aphthae, and osteogenic changes. Patients benefit even more, when oral health professionals collaborate with other healthcare providers (e.g. physicians, nutritionists, etc. to identify changes in vascularity, and provide treatment or alter the treatment of xerostomia, GERD, dysgeusia (when possible), aphthae, osteogenic changes, and changes in vascularity.