Never in history has so much attention been paid to human movement. Global migration yields demographic shifts of historical significance, profoundly shaking up world politics – as shown by the “refugee crisis,” the rise of White nationalism in the United States, and the spreading of the populist right in Europe. Global migration is one of the defining issues of the 21st century, challenging the fabric of Western societies, remodeling the essence of sovereignty, and changing the way we think of borders and boundaries. The article puts forward ten reasons why international migration is one of the greatest challenges of our time. The ten reasons are related to fundamental changes in the patterns of migration, in Western societies, and in the world as a whole. Indeed, migration will be at the center of world politics in the years to come.