"Objective/Context: This article addresses the systemic and macro-historical meaning of the position of Brazil in South America. We argue that the Brazilian predominance was an outcome of structural changes in the regional system.Methodology: We trace the process of formation of the South American regional system in the post-independence period, identifying four intervals of regional structural transformation: 1) anarchical system formation (1810-1870s); 2) anarchical stability (1880-1930s); 3) hegemonic transition (1940-2000s); and 4) hegemonic stabilization (2000-2010s). Process tracing and historical-comparative methods help to organize the corresponding causal chains.Conclusions: Our findings show that Brazil’s role in the region is the result of an ongoing process of regional hegemonic stabilization, characterized by (i) a unipolar distribution of power, (ii) a regional governance order, and (iii) a hegemonic ordering principle. Despite the existence of structural conditions for the configuration of a hegemonic structure, the country did not embrace its position as a regional hegemon.Originality: While the literature on the topic mainly focuses on foreign policy and interactional dynamics, this study proposes an explanation focused on regional structural changes, presenting: (i) a theory of systemic complexity and macro-historical changes, and (ii) a theory of systemic structure types, addressing relations between distinct structural elements at the regional level of analysis."