Mycoplasma genitalium has emerged over the last 30 years as a sexually transmitted infection (STI). As data have accumulated, our understanding of this pathogen and its role in disease continues to evolve. This in turn creates new challenges and complexities. Questions remain regarding the natural history of M. genitalium, its contribution to disease and long-term sequelae. A decline in cure rates for first-line anti-microbials has been observed. This is likely in part due to high usage of single-dose azithromycin in the sexual health field but also due to the intrinsic ability of M. genitalium to rapidly acquire anti-microbial resistance. Consequently, the term 'the new STI superbug' is not infrequently used by the media to describe this pathogen. Currently available antibiotics have side effects that, though rare, are potentially serious. This leads to inherent questions regarding the benefit of testing for and treating M. genitalium, particularly in asymptomatic individuals or in genital syndromes where the benefit of treatment is not well established. In this review, we summarize the most recent evidence and literature regarding M. genitalium and explore areas of research where disparities exist. We discuss the contribution of M. genitalium to genital syndromes, particularly those where data are conflicting, in order to inform indications for testing and treatment. Avoidance of increasing anti-microbial resistance with astute anti-microbial stewardship is paramount if we are to successfully manage M. genitalium infection. We examine the state of play regarding anti-microbial resistance and how to combat this, including currently available anti-microbials, resistance-guided therapy and novel therapeutic approaches. We aim to provide an overview of the current understanding of M. genitalium and the implications for current clinical practise and suggestions for future research.