Regionalism in international relations refers to the process through which states within a particular geographical area come together to pursue common objectives, establish institutions, and cooperate in political, economic, cultural, or security matters. It represents a middle ground between nationalism, which emphasizes the primacy of the sovereign state, and globalism, which stresses universal cooperation. Regionalism can manifest in diverse forms such as economic blocs, security alliances, and cultural or political unions, with examples including the European Union (EU), the Association of Southeast Asian Nations (ASEAN), and the African Union (AU). The concept embodies both a political project and a social process where shared identity and interests are articulated to strengthen regional solidarity and collective action. Theories of regionalism can be broadly understood through different perspectives in international relations. One of the earliest theoretical approaches is functionalism, which argues that cooperation in technical and economic sectors can spill over into political areas, thereby reducing conflict and promoting integration. Functionalists emphasized practical cooperation in non-controversial areas like transport or health, assuming it would create habits of working together. Closely related is neo-functionalism, associated with Ernst Haas, which focuses on the idea of “spillover.” It suggests that integration in one area, such as trade, inevitably pushes states to integrate further in other sectors, eventually creating a supranational structure. The European Union is often analyzed through the neo-functionalist framework. On the other hand, intergovernmentalism presents a state-centric critique of neo-functionalism.