Between 1873 and 1945 Japan and Mongolia had a complex and important relationship that has been largely overlooked in post-war studies of Japan’s imperial era. In fact, Japanese-Mongolian relations in the modern period provide a rich field of enquiry into the nature of Japanese imperialism as well as further evidence of the complexity of Japan’s relationships with other Asian countries in the decades before 1945. This thesis examines the relationship from the Japanese perspective, drawing on a diverse range of contemporary materials, both official and unofficial, including military documents, government reports, travel guides and academic works, many of which have been neglected in earlier studies. In previous analyses, the strategic dimension has been seen as overwhelming and Mongolia has often been regarded as merely a minor addendum to Japan’s relationship with Manchuria. In fact, however, Japan’s connection with Mongolia itself was a crucial part of its interaction with the Chinese continent from the 1870s to 1945. Though undeniably coveted for strategic reasons, Mongolia also offered unparalleled opportunities for the elaboration of all the major aspects of the discourses that made up Japan’s evolving claim to solidarity with and leadership of Asia. It also functioned as a showcase for Japan’s supposedly benevolent intentions towards Asia. In some ways, moreover, the relationship with Mongolia was presented as distinctive, particularly because of the common faith in Buddhism and a supposedly shared ancestry in ethnic terms. In turn, the military, political, ideological and cultural opportunities apparently provided by Mongolia account for the wide range of groups and individuals in Japan that developed Mongolian connections and for the often close relations between these groups and individuals on the one hand, and the most powerful institutions of the Japanese state on the other.