Labor is one of the few and often most critical assets of the poor. Making better employment opportunities available to the poor is one of the main paths to escape poverty. Increasing labor mobility--whether internally or across borders--is one of the surest ways to connect the poor to better jobs, and is a key part of the development process. This Policy Research Report provides an overview of the main patterns of labor mobility across the world, and explores how the movement of people across national boundaries affects labor market outcomes such as wages and employment in both origin and destination labor markets. Areas of policy interest that have previously received too little rigorous economic analysis will also be covered, including human capital acquisition, female labor force participation, the role of refugees, and the circulation of global skills. The report will aid policy makers in assessing the economic implications of labor mobility and contribute to the design of welfare and productivity-enhancing policy tools.