The emergence of cryptographically relevant quantum computing presents a strategic governance challenge for national security because contemporary digital infrastructures depend extensively on public-key cryptographic mechanisms whose long-term security may be threatened by sufficiently capable quantum computers. This research examines post-quantum cryptographic governance as a policy, risk-management, interoperability, and implementation problem rather than solely as a cryptographic algorithm-selection exercise. The study adopts a conceptual research-and-review methodology based exclusively on the supplied literature, using insights from security and privacy, interoperability, digital transformation, standards-based architectures, and emerging technology governance to construct an integrated post-quantum governance framework. Particular attention is given to cryptographic inventory, risk prioritization, migration governance, interoperability, institutional accountability, lifecycle management, and national-security continuity. The analysis indicates that post-quantum readiness requires coordinated governance across technical and organizational layers, with migration decisions guided by asset criticality, data longevity, dependency relationships, and operational constraints. The study further argues that interoperability principles are central to post-quantum migration because cryptographic transitions must coexist with heterogeneous legacy systems and distributed information environments. The proposed framework therefore combines risk assessment, policy development, technical migration, validation, monitoring, and institutional oversight. The research contributes a governance-oriented perspective in which cryptographic agility and standards-based interoperability become strategic national-security capabilities rather than isolated technical controls.