Starting with the so-called Uganda Controversy of 1905, the Jewish Territorialists searched for areas outside Palestine on which to create settlements of Jews. This study analyses both Territorialist ideology, and the place the movement occupied within a broader Jewish political and cultural narrative during the first half of the twentieth century. It also shows Territorialism's relevance beyond a specifically Jewish historical analytical framework: Territorialist thought and discourse reflected several more general contemporary geopolitical trends and practices. The most notable of these trends was inspired by the international policymakers' (post-)colonial approach to peoplehood, territory and space, before, but also directly following the Second World War. This approach relied on notions and practices like migration, colonialism and colonisation, biopolitics, agro-industrial science, as well as "(empty) spaces" and un(der)developed territories. Studying Territorialism, therefore, helps to shed new light on both Jewish political history, and on the evolution of modern geopolitical thinking. The empirical emphasis of this study is on the second wave of Territorialism, which commenced in the mid-1930s and was mainly represented by the Freeland League for Jewish Territorial Colonisation. This period ended sometime in the mid 1960s, with the Freeland League abandoning its Territorialist activities in favour of Yiddish cultural work. Despite this focus on the later phase of Territorialism, the Freeland League's origins lay with Israel Zangwill's Jewish Territorial Organisation (ITO, 1905-1925). As Zangwill's legacy was still strongly felt in the Freeland-days, an exploration of these Territorialist origins forms part of this analysis as well. Lastly, the movement's ideological direction was defined by a handful of intellectuals: Zangwill in the ITO-days; Ben-Adir, Joseph Leftwich, and, most importantly, Isaac N. Steinberg in the Freeland League-era. Therefore, the lives and works of these people, as well as the archival material they left behind, are central to this dissertation.