The Joint United Nations Programme on HIV/AIDS (UNAIDS) 90-90-90 global treatment target aims to achieve 73% virologic suppression among HIV-infected persons worldwide by 2020.To estimate the clinical and economic value of reaching this ambitious goal in South Africa, by using a microsimulation model of HIV detection, disease, and treatment.Modeling of the "current pace" strategy, which simulates existing scale-up efforts and gradual increases in overall virologic suppression from 24% to 36% in 5 years, and the UNAIDS target strategy, which simulates 73% virologic suppression in 5 years.Published estimates and South African survey data on HIV transmission rates (0.16 to 9.03 per 100 person-years), HIV-specific age-stratified fertility rates (1.0 to 9.1 per 100 person-years), and costs of care ($11 to $31 per month for antiretroviral therapy and $20 to $157 per month for routine care).South African HIV-infected population, including incident infections over the next 10 years.Modified societal perspective, excluding time and productivity costs.5 and 10 years.Aggressive HIV case detection, efficient linkage to care, rapid treatment scale-up, and adherence and retention interventions toward the UNAIDS target strategy.HIV transmissions, deaths, years of life saved, maternal orphans, costs (2014 U.S. dollars), and cost-effectiveness.Compared with the current pace strategy, over 5 years the UNAIDS target strategy would avert 873 000 HIV transmissions, 1 174 000 deaths, and 726 000 maternal orphans while saving 3 002 000 life-years; over 10 years, it would avert 2 051 000 HIV transmissions, 2 478 000 deaths, and 1 689 000 maternal orphans while saving 13 340 000 life-years. The additional budget required for the UNAIDS target strategy would be $7.965 billion over 5 years and $15.979 billion over 10 years, yielding an incremental cost-effectiveness ratio of $2720 and $1260 per year of life saved, respectively.Outcomes generally varied less than 20% from base-case outcomes when key input parameters were varied within plausible ranges.Several pathways may lead to 73% overall virologic suppression; these were examined in sensitivity analyses.Reaching the 90-90-90 HIV suppression target would be costly but very effective and cost-effective in South Africa. Global health policymakers should mobilize the political and economic support to realize this target.National Institutes of Health and the Steve and Deborah Gorlin MGH Research Scholars Award.