Historians of science have long thought about translation primarily as a metaphor for the Kuhnian incommensurability of worldviews, or as a task of repackaging technical information in popular form. The abandonment of crude anti-positivism and of a diffusionist model of knowledge have discredited both approaches to translation. We are interested instead in bringing history of science into dialogue with translation studies and histories of the politics of language use. We draw on recent work on science and nationalism and on the mobility of knowledge in an age of globalization. We are interested particularly in how a modern language—whether French, German, Russian, or English—becomes an international scientific language. What is “lost in translation” in this process? How do “small languages” respond? What are the consequences for communication between scientists and the public? These are ultimately questions about what science is and whom it should serve. Is science best seen as universal knowledge or as a cultural achievement? Should science national interests or the interests of humanity? Is an international scientific language necessarily a jargon accessible only to experts? We address these questions through case studies drawn largely from the multilingual context of central and eastern Europe in the second half of the nineteenth century, the early age of scientific internationalization. As these examples show, the language politics of the Russian and Austrian empires had global ramifications, informing strategies alternately for establishing and undermining international scientific organizations. The implications of these studies should be of interest to historians studying science and technology, nationalism, colonialism, and globalization.