The objective of this article is to estimate the prevalence of HIV among men who have sex with men (MSM) who frequent gay social venues and to describe the characteristics of MSM infected with HIV. In 2015, the PREVAGAY study collected, in a cross-sectional, anonymous, and random manner, behavioral questionnaires and blood samples from MSM frequenting bars, saunas, and backrooms in five French cities. Testing for HIV antibodies was performed in the laboratory using the Genscreen ultra HIV Ag-Ab® test (Biorad); positive samples were confirmed by serotyping and/or Western Blot. Among the positive samples, antiretroviral treatment status was assessed. A total of 2,646 MSM agreed to participate. The prevalence of HIV was estimated at 14.3% (95% CI: [12.0–16.9]). It varied by city and age group. It stood at 4.4% among those under 25 years of age. Among HIV-positive MSM, 91.9% had been diagnosed, and 94.9% of those were on treatment. In this population, HIV prevalence was high and condom non-use was significant. Nevertheless, the proportions of MSM who were diagnosed and on treatment were high. These results underscore the need to continue preventive efforts in gay social venues. The prevalence of HIV among young MSM necessitates the consideration of additional interventions that are closely aligned with their lifestyles.