International trade in the twenty-first century has shifted considerably away from classical multilateral mechanisms toward more flexible regional cooperation frameworks. RCEP, covering fifteen Asia-Pacific nations with 2.2 billion people and 29.6% of global GDP, is among the most consequential expressions of this development. Prior studies have examined RCEP through either quantitative-economic or diplomatic lenses separately, leaving an integrative analysis of its structural-legal characteristics, geopolitical dynamics, and technological dimensions largely absent from the literature. This study analyzes the structure, mechanisms, and implications of RCEP for the global trading system, applying a normative-juridical method with a descriptive-qualitative orientation through content analysis of official RCEP documents, WTO publications, and academic literature from 2015 to 2023. Two principal findings emerge. First, RCEP has reoriented international trade governance from a universalist-multilateral model toward a flexibility-based plurilateral one, reflected in its differentiated treatment of member economies, its modified single-undertaking approach, and its consensus-driven legal framework. Second, RCEP functions as a complement to the WTO while serving as a testing ground for multilateral trade reform, responding simultaneously to knowledge-based economic demands through provisions on electronic commerce and cross-border data protection. Geopolitically, the agreement generates structural incentives for sustaining stability among China, Japan, and South Korea. This study concludes that RCEP represents a systemic evolution in international trade governance, offering a paradigm that is more inclusive, adaptive, and responsive to the political-economic complexities of the twenty-first century.