STUDY OBJECTIVE: The aim of this paper is to review our understanding of the vaginal microbiome (VM), the internal and external factors that influence its composition, and how it relates to adult and adolescent reproductive health. METHODS: A literature review was conducted in March 2024 using Web of Science, PubMed, Embase, and Google Scholar. RESULTS: The majority of studies focused on the VM in healthy adult women and demonstrated that the VM changes across the menstrual cycle, with the greatest species diversity during menses. In most women, the VM is dominated by lactobacilli, however, Black and Hispanic women are more likely to demonstrate a polymicrobial profile. The VM is also affected by lifestyle factors (e.g., diet, alcohol, smoking, sexual activity, vaginal hygiene) and contraception, whereas the role of endogenous reproductive hormones in shaping the VM is unclear. The VM of adolescents begins to resemble that of adults in mid- to late puberty. CONCLUSION: The VM is a complex and dynamic microbial community that has the potential to serve as an important clinical biomarker of adult as well as adolescent reproductive health, possibly aiding in the diagnosis of such conditions as polycystic ovarian syndrome. However, additional studies are needed in healthy adolescent girls.