As countries ravaged by colonial capitalism and white supremacy sought to build a post-imperial world, many turned to socialism to offer a new vision of social equity and post-colonial development. While development is often understood as a process that emerges from the Global North to the Global South, this book examines the history of development from the perspective of Asia, Africa, and Latin America, centering how socialism was employed to drive post-colonial development projects. Beginning in the interwar era, Socialism, Internationalism, and Development in the Third World rewrites the origins of development by examining dialogues about race, class, and uneven development between the North and South. Focusing on the 1950s and 1960s, it explores decades of aid competition, cooperation and solidarity across the Global South, particularly among the Left, to show how countries across the Global South consciously developed internationalist efforts to cooperate and connect with each other, developing shared regional and global frameworks for development and self-reliance. This book brings fresh angles to the history of socialism, development, and internationalism by viewing them as intertwined narratives from the perspective of the Global South.