This article analyzes the discovery of Chagas disease and the parasite that causes it (Trypanosoma cruzi) by Carlos Chagas in 1908/1909, with a special focus on the scientific and social context in which this occurred. Its inclusion in the international debate on European tropical medicine--especially with researchers from the German school of protozoology--and its connection with discussions on the modernization of the recently established Brazilian Republic are also examined. The discovery of Chagas disease became a decisive aspect in the scientific project that Oswaldo Cruz sought to establish at the institute that bears his name. It was extolled as a symbol of Brazil's scientific ability t produce knowledge in line with the international scientific agenda, while simultaneously being attuned to the specific problems of the country.