This study introduces Dung’s Tourism Balance Index (TBI) and Inbound–Outbound Balance (IOB) as the first bounded, theory-driven, and globally comparable indicators of international tourism equilibrium. No prior academic or institutional framework has quantified tourism trade balance in this symmetric, normalized form. By converting absolute monetary flows into coherent equilibrium metrics, TBI and IOB establish a new paradigm for evidence-based analysis and policy-making in global tourism. This contribution lays the foundation for a next-generation governance framework grounded in structural balance rather than gross receipts.