The Lesotho Population-based HIV Impact Assessment (LePHIA) survey was conducted nationally and designed to measure HIV prevalence, incidence, and viral load suppression (VLS). A nationally representative sample of 9,403 eligible households was surveyed between November 2016 and May 2017; analyses account for study design. Consenting participants provided blood samples, socio-demographic and behavioral information. Blood samples were tested using the national rapid HIV testing algorithm. HIV-seropositive results were confirmed with Geenius supplemental assay. Screening for detectable concentrations of antiretroviral (ARV) analytes was conducted on dried blood specimens from all HIV-positive adults using high-resolution liquid chromatography coupled with tandem mass spectrometry. Self-reported and/or ARV biomarker data were used to classify individuals as HIV-positive and on treatment. Viral load testing was performed on all HIV-positive samples at central labs. VLS was defined as HIV RNA < 1000 copies per mL. Overall, 25.6% of adults ages 15-59 were HIV-positive. Among seropositive adults, 81.0% (male: 76.6%, female: 84.0%) reported knowing their HIV status, 91.8% of people living with HIV (male: 91.6%, female: 92.0%) who reported knowing their status reporting taking ARVs, and 87.7% (male and female: 87.7%) of these had VLS. Younger age was significantly associated with being less likely to be aware of HIV status for both sexes. Findings from this population-based survey provide encouraging data in terms of HIV testing and treatment uptake and coverage. Specific attention to reaching youth to engage them in HIV-related intervention is critical to achieving epidemic control.