This Element argues that settlers from Western Europe shaped European state formation and transformed the political and economic fate of Eastern Europe and Scandinavia between 800 and 1800. While existing work on European colonization focuses on overseas settlers, and studies of Europe's development tend to concentrate on the continent's western regions, the Element highlights a significant internal wave of settlement from Western to Eastern and Northern Europe. Beginning around 1100 and tapering off after 1400, this settler movement spurred economic development and the spread of local self-government across Eastern Europe and Scandinavia. Settlers also provided institutional templates that local rulers adapted in their efforts to build states. These rulers were increasingly compelled to bargain with politically autonomous and large cities. Over time, the emergence of new states in Eastern Europe intensified geopolitical competition across the continent.