In the United States, gay, bisexual men, and men who have sex with men (MSM) represent 86% of new HIV infections among males. Approximately 1 in 7 men with HIV are unaware of their HIV status (CDC, 2017, 2019a, 2020a). To explore influences on MSM HIV risk behavior, the authors performed a systematic review of quantitative studies conducted in the U.S. assessing what is purported as masculinity. From 30 identified studies, significant findings were framed within the Social Ecological Model (SEM) levels (e.g., Individual, Relationship, Community). SEM level themes were applied to create the Masculinity 10, a preliminary 10-item assessment to explore the influence of masculinity on MSM HIV risk behavior. To increase MSM engagement in HIV prevention and treatment, the influences of masculinity (e.g., attitude toward sexual minorities, appearance, emotion, temperament, substance use, sexual activity, social support, intimate relationships, health care) on HIV risk behavior should be further explored.