In the aftermath of the Cold War, the field of international security has evolved from predominantly state-centric and military-focused paradigms toward a more comprehensive, multidimensional analytical approach. In this context, the inclusion of identity, economic factors, environmental concerns, migration, and societal stability has expanded the conceptual boundaries of security and necessitated the reconfiguration of theoretical approaches. Within this transformation, the Regional Security Complex Theory (RSCT), developed by Barry Buzan and Ole Waever, offers a distinctive contribution by emphasizing that security is primarily structured at the regional level. RSCT posits that security interactions cluster according to geographic proximity, with threat perceptions most acutely constructed among neighboring actors, while interdependence generates distinctive regional patterns. The theory conceptualizes security across military, political, economic, societal, and environmental sectors, providing an analytical platform compatible with an expanded notion of security. Theoretically, RSCT synthesizes the neo-realist focus on distribution of power, structural constraints, and competition with the constructivist insights into identity, perception, discourse, and securitization processes. This integrated approach enables a comprehensive analysis of security dynamics that accounts simultaneously for material power factors, structural imperatives, and the social construction and legitimation of threats. This chapter proceeds from the premise that structural transformations following the Cold War necessitate evaluating security not solely at the global level, but also through the lens of regional interaction patterns. By examining the theoretical debates between traditional and widener security approaches, it highlights the transition from state-centric paradigms to multisectoral conceptions of security. The assessment conducted through variables such as regional polarization, great power influence, and securitization processes reveals the increasing analytical importance of the regional level. Consequently, the study argues that the BGKT offers a robust, flexible, and integrative theoretical framework for understanding contemporary security dynamics.