Hepatitis B Virus (HBV) infection is a severe viral condition that causes inflammation of the liver and affects how well the liver functions. HBV infection has a worldwide distribution. Hepatitis D Virus (HDV) requires the HBV surface protein (HBsAg) to reproduce and a high rate of HBV infection to accomplish prevalent.HDV in patients also infected with HBV results in worst outcomes than infection with HBV alone. Considering the enormous problems associated with Co-infection of HBV and HDV patients, it became imperative to develop a mathematical model of HBV-HDV Co-infection with controls to help proffer solutions to those enormous problems. Many mathematical models exist for HBV, but little or none is available for HBV-HDV Co-infection. In this book, the etiology of both HBV and HDV as well as their Co-infection were studied. Furthermore, a mathematical model of HBV-HDV Co-infection with controls (incorporating enlightenment, use of condom and therapy) was built and analysis on the model carried out including simulations, valid and useful results were obtained. WHO, CDC, Epidemiologist, students in tertiary institutions and researchers in Maths modeling will find this text useful.