This chapter scrutinises the causes, effects, and policy implications of migration within a globalised economy. We explore the drivers of migration, such as income disparities, labour market opportunities, and geopolitical factors, and analyses the economic contributions of migrants to host and origin countries. The chapter discusses theoretical frameworks, including the gravity model and human capital theory, to explain migration flows and their impacts on labour markets, public finances, and social cohesion. It highlights the dual effects of migration, such as addressing labour shortages and innovation in host economies while also creating challenges related to integration and social tensions. The chapter evaluates policies, including visa systems, integration programmes, and remittance facilitation, designed to manage migration effectively. Empirical methods, such as zero-inflated models and difference-in-difference approaches, are employed to assess migration trends and impacts. By integrating theory, evidence, and policy, the chapter sheds light on the complexities of migration in shaping national and global economic outcomes.