Decision Architecture™ introduces a management discipline focused on the deliberate design of organisational decision systems. Rather than treating decisions as isolated managerial events, this foundational paper argues that sustainable organisational performance depends on how decision rights, governance, information flows, escalation logic, feedback loops, and organisational learning are intentionally designed. The work establishes the theoretical foundations of Decision Architecture™, defines its core principles, and provides a conceptual framework for future academic research and executive practice.