This book provides a comprehensive exploration of how Information Technology can transform to meet the urgent demands of sustainability in the digital age. It emphasizes green computing as a pivotal enabler of net-zero goals, addressing the pressing challenges of high energy consumption, carbon emissions, and electronic waste generated by traditional IT practices. The book blends theory, research, and practical applications to present strategies for achieving sustainable IT. Core topics include energy-efficient hardware design, AI-driven optimization, cloud and edge computing, green data centers, renewable energy integration, sustainable software development, and circular economy models. It also examines global standards, policies, compliance frameworks (ESG, CSR), and real-world case studies that highlight both challenges and opportunities in adopting green IT solutions. By tracing the historical evolution of sustainable IT practices from early awareness in the 1970s to modern cloud and AI-driven approaches the book illustrates how organizations can embed sustainability into the entire IT lifecycle: design, operation, and disposal. It stresses that green IT is not only an environmental necessity but also a strategic advantage, enhancing operational efficiency, reducing costs, and boosting corporate reputation. Designed for students, researchers, industry practitioners, and decision-makers, the book serves as both an academic reference and a practical guide. Ultimately, it envisions a future where technology and sustainability progress hand in hand, making IT a powerful catalyst for achieving global climate action and net-zero ambitions.