Mycobacteria are bacterial pathogens which cause diseases in humans and non-human animals. This monograph will primarily cover the most important and widely researched groups of mycobacteria: members of the Mycobacterium tuberculosis complex (MTC) and Mycobacterium leprae, across a wide range of host species. M. tuberculosis and M. bovis are particularly relevant with the increasing drug resistance and co-infection with HIV and the possible cross-infection of badgers and cattle associated with M. bovis. This ideal reference for researchers working in different fields draws together information on different pathogens, and by considering the diseases in a zoonotic context provides a One Health approach to these important groups of diseases.