Quantum Frontiers: Applied Technologies for Industry, Defense and Society presents a practical, application-first view of how quantum science is moving from labs into real-world systems. Opening with a clear primer on principles, platforms (superconducting circuits, trapped ions, photonics, etc.) and roadmaps, the book equips readers with the vocabulary and expectations needed to evaluate claims of quantum benefit. Subsequent chapters examine domain-specific opportunities: quantum simulation for climate and weather modeling; quantum-enabled materials and energy design; quantum approaches to water treatment and desalination; and applied optimization for finance, logistics and autonomous mobility. Security and defense are addressed candidly-covering cryptography, migration to post-quantum standards, secure cloud and voting architectures, and dual-use governance. The role of sensing and monitoring for resilient infrastructure is explored, alongside privacy and oversight concerns. The closing chapter on governance offers standards, policy tools, ethics and sustainable-development perspectives to guide equitable deployment. Throughout the book the emphasis is on engineering reality: cost, manufacturability, energy use, evaluation frameworks, and concrete pilot recommendations. Designed for students, engineers, managers, policymakers and citizens, the book combines conceptual grounding with practical exercises, readings and decision checklists. Its tone is pragmatically optimistic: quantum tools hold promise, but realizing that promise demands careful engineering, honest assessment and broad collaboration.