P>Bacterial vaginosis (BV) is the most common vaginal infection among women of childbearing age. This condition is notorious for causing severe complications related to the reproductive health of women. Five decades of intense research established many risk factors for acquisition of BV; however, because of the complexity of BV and lack of a reliable animal model for this condition, its exact aetiology remains elusive. In this manuscript, we use a historical perspective to critically review the development of major theories on the aetiology of BV, ultimately implicating BV-related pathogens, healthy vaginal microbiota, bacteriophages and the immune response of the host. None of these theories on their own can reliably explain the epidemiological data. Instead, BV is caused by a complex interaction of multiple factors, which include the numerous components of the vaginal microbial ecosystem and their human host. Many of these factors are yet to be characterized because a clear understanding of their relative contribution to the aetiology of BV is pivotal to the formulation of an effective treatment for and prophylaxis of this condition.