In July 2012, tenofovir disoproxil fumarate-emtricitabine (TDF-FTC, brand name Truvada) was approved by the Food and Drug Administration (FDA) to prevent HIV infection. To estimate the extent of the US government's direct financial contribution to the discovery and development of Truvada, we identified National Institutes of Health awards using FDA documents, peer-reviewed literature, patent records, court filings, and other publicly available materials. We classified seventy-three federal government awards to eleven researchers as being directly linked to the development and clinical testing of Truvada for prevention therapy, through which the US government spent an estimated $143 million. The substantial public funding raises questions about the high price charged by the drug's manufacturer, which reduced its affordability and limited its accessibility as HIV preventive therapy.