Comparative regionalism constitutes a new frontier of international relations analysis that provides a more focused theoretical lens for understanding the localized phenomena dominant in international politics. However, as is often the case with a relatively new area of academic inquiry, the subfield currently suffers from a number of challenges in conceptual agreement and operationalization conventions that have slowed progress. Having perhaps finally caught up with area specialists and researchers in the field of comparative politics in recognizing the relative importance of regional spaces, the question remains as to how to most effectively understand the extent regions—as either levels of analysis or units unto themselves—are substantively integral in generating the outcomes studied by international relations scholars. Following almost four decades of theorizing, future steps lie in clearer conceptual definitions followed by generating novel empirical findings that may complement, or contradict, existing international relations theories. While some early attempts at engaging comparative regionalism exist prior to the Cold War’s conclusion, most theorizing begins at the point at which the region as a concept is able to emerge from the shadow of international relations research’s emphasis on the bipolar order of the American–Soviet rivalry. These early explorations, however, were frequently limited to either qualitative discussion of emerging trading behaviors and political institutions or, alternatively, the exploration of “non-Western” types of political engagement that challenged the traditional Anglo-European understanding of both international relations and the conduct of political science. Building on the backdrop of this conceptual theorizing, empirical work highlighting regional distinctions began to emerge as well. This renewed emphasis on comparing regional spaces is often undertaken from a small-N comparative methodological approach to identify similarities and differences between regions, with a very specific interest in developing an understanding for the causal variation behind how regional spaces’ trajectories develop and diverge. Finally, one of the greatest theoretical challenges of comparative regionalism is the applicability of theories designed to understand the interactions of the entire international system (with primary focus on the major powers) to more localized spaces and conflicts. This is not to claim that politics necessarily follows different rules within different regions, but instead that because regional-local contexts are sufficiently unique, the combination of causal variables present may lead to very different outcomes for many phenomena of interest that scholars seek to understand. As regional importance has risen over the past 20 years, a clear set of criteria upon which theoretical development and empirical analysis can proceed is required in order to delineate the effects of regions on states and international politics.