Mycoplasma genitalium is an emerging pathogen that has been detected in the male and female reproductive tracts. It is an established cause of nongonococcal urethritis and evidence linking it to cervicitis, endometritis, and tubal factor infertility is accumulating. Whether a pathogen is sexually transmitted has important implications for clinical management because partner management strategies are an essential part of the treatment plan for sexually transmitted infections. However, mere detection in the genital tract and associations with reproductive tract disease are insufficient to conclude that an organism is sexually transmitted. Therefore, to assess whether M. genitalium is sexually transmitted, we evaluated the literature in terms of associations with established risk factors for other sexually transmitted infections, comparisons of sexually experienced individuals to nonsexually experienced individuals, consideration of other modes of transmission, assessment of concordant infection status among sexual partners, and examination of molecular strain typing in concordantly infected partners.