Medical Mercenaries and Transimperial Science traces the trajectories of some 300 physicians from German-speaking Switzerland, Habsburg Austria, and the German Empire who served in the Dutch East Indies’ military and civil medical institutions between the 1870s and 1920s. The book offers new insights into the transimperial networks that shaped medicine in the late nineteenth and early twentieth centuries, highlighting the crucial yet ambivalent role of foreign physicians in the Dutch Empire. It shows how colonial medicine functioned as a vehicle for performing bourgeois respectability, scientific authority, and imperial masculinity, all while constantly being challenged and renegotiated in light of unfamiliar diseases, indigenous expertise, and local resistance. Following German-speaking physicians across the colonial military, laboratories, and plantations, the study reveals how colonial medicine structured hierarchies of race, class, gender, and nationality, and how knowledge forged in the tropics reshaped metropolitan medical discourse in German-speaking Europe and beyond.