**Abstract**

The actinobacteria have an important role to play in humans. On one hand the actinobacteria, especially the *streptomyces spp.* are used medicinaly for synthesis of some novel anti-microbial medicines whilst on the other hand, *Actinomyces species* also exist as normal commensals as well as pathogens that cause disease in humans. The bacteria play a role in the maintenance of healthy human organs where they are considered normal inhabitants. The genus, *Actinomyces* is normally found in the mouth, gut and the female genital tract of human beings. This chapter elaborates on different clinical manifestations of actinomycosis in humans, making use of visual illustrations depicting the vast array of pathology therein. Finally, the diagnosis and treatment of these infections in humans is also fully discussed.

**Keywords:** actinomycosis, clinical phenotypes, diagnosis, and treatment
