This book provides a new, more complex definition of Third Worldism by exploring the dynamic collaborations between Europe and the Global South in response to colonialism. It focuses on how transnational initiatives surpassed Eurocentric limitations, highlighting Europe's role in decolonization efforts and the Global South's anti-colonial activism within European territories. By doing so, the book reveals how the Global South became central to new understandings of decolonial modes. The volume critically addresses contemporary decolonial debates, tracing the history of Third Worldism and its leftist and Catholic roots in Europe. It sheds light on key themes such as the architectural embodiment of cooperation, Ghana's alternative economic projects, and non-Western epistemologies. By reframing the debate on Third Worldism, this book adds to the academic discourse, offering fresh perspectives on the solidarity and cooperation between the Global North and South. It will appeal to students, researchers, and scholars of international relations, political science, law, and history and an audience interested in a better understanding of Third Worldism and the connected historical and contemporary political landscapes.