This comprehensive work explores the transformative evolution of AI from passive tools to autonomous agents capable of independent decision-making and goal-oriented behavior. It examines how agentic AI systems, distinguished by their autonomy, adaptability, and strategic capabilities, are revolutionizing industries from healthcare to smart cities. The book provides a thorough exploration of foundational concepts, core frameworks including multi-agent systems and reinforcement learning, and critical ethical considerations. Through detailed case studies and real-world implementations across healthcare, finance, industrial automation, education, and cybersecurity, readers gain both theoretical understanding and practical insights. The book concludes with forward-looking perspectives on policy, regulation, and human-AI collaboration, making it an essential resource for researchers, professionals, and policymakers in the rapidly evolving field of artificial intelligence.