The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services (HHS), is the Nation’s primary medical research agency, making important discoveries that improve health and save lives. NIH conducts and supports a comprehensive program of basic, behavioral, clinical, and translational research on HIV/AIDS and its associated coinfections, comorbidities, and other complications. Since HIV crosses nearly every area of medicine and scientific investigation, the response to the HIV pandemic requires a multi-Institute, multidisciplinary, global research program. At NIH, this research is coordinated by the Office of AIDS Research (OAR) and carried out by nearly all the NIH Institutes and Centers, in both at NIH and at NIH-funded institutions worldwide. The NIH HIV/AIDS Research Program represents the world’s largest public investment in AIDS research. Within NIH, the National Institute of Allergy and Infectious Diseases (NIAID) manages the largest portfolio of HIV/AIDS research activities. NIAID-supported investigators have made groundbreaking scientific discoveries that have led to significant progress in the fight against HIV/AIDS. Among these discoveries, NIAID-supported research has demonstrated that people living with HIV who take antiretroviral medications daily as prescribed and who achieve and maintain an undetectable viral load have effectively no risk of sexually transmitting the virus to an HIV-negative partner.