Sexually transmitted infections (STIs) refer to a broad array of pathogens that are transmitted through vaginal, anal, or oral sex. While STI case rates are highest in adolescents and young adults, the most serious health outcomes occur later in life and are disproportionately borne by women and infants. For these reasons, STI prevention and control is an important public health investment for every country. This chapter summarizes the global epidemiology of STIs and their associated health consequences, and reports on factors affecting STI spread in the community. It also discusses STI prevention and control as a public health intervention, relying on many interrelated interventions working together to reduce STI incidence and prevalence in the community. Finally, it considers some of the most likely challenges and opportunities in STI prevention anticipated over the next few decades.