This chapter examines migration as a central geopolitical and social phenomenon in the twenty-first century, no longer a peripheral issue but a key driver of global power dynamics. Migration reflects structural imbalances—conflict, persecution, economic collapse, and climate crises—but is increasingly treated strategically by states as a tool for demographic leverage, labour supply, or political pressure. Migratory flows are complex and multidirectional, with intraregional movements as significant as South-to-North migration. The chapter highlights the “weaponization of migration,” where states exploit population movements to influence other countries, as seen in Turkey, Belarus, and Morocco. Borders are increasingly externalized, with transit countries acting as buffer zones in exchange for aid, creating a legal and humanitarian gray zone that complicates migrants’ protection. Migration also serves economic purposes: developed nations use it to address labour shortages and aging populations, while sending countries benefit from remittances, sometimes constituting a major part of GDP. Yet, migration is a potent domestic political issue, fuelling populism, polarization, and identity debates. Climate change is projected to become a major driver of future displacement, with millions at risk of forced migration, yet international law does not recognize climate refugees. The chapter concludes that migration is both a symptom and catalyst of global inequalities and instability. Managing it requires coordinated, long-term, rights-based, and multilateral approaches, making migration central to twenty-first-century geopolitics.