The mainframe - a powerful, resilient, and secure computing platform - is at the heart of many global businesses, handling immense volumes of transactions daily. However, in today's rapidly evolving technological landscape, maintaining efficiency and competitiveness requires modernization. This imperative has brought continuous integration and continuous deployment (CI/CD) practices into the limelight, extending even to the world of mainframes. This book, "Modernizing Mainframes: A Comprehensive Guide to Implementing Continuous Integration and Continuous Deployment (CI/CD)", is designed to bridge the gap between traditional mainframe operations and the accelerating world of DevOps. It provides the readers with an understanding of how they can bring the speed and agility of CI/CD into their mainframe environments without compromising on the security, stability, and scalability that mainframes offer. Written with a diverse audience in mind, this book aims to assist IT professionals, DevOps engineers, mainframe experts, and decision-makers as they navigate the transformation journey. By combining comprehensive theoretical knowledge, practical steps, real-life examples, and future trends, it provides a foundation to implement, adapt, and optimize CI/CD practices in mainframe environments. The book begins with a review of the basics of mainframes and CI/CD, setting the stage for the detailed discussions that follow. It then delves into the specific challenges and benefits of implementing CI/CD in a mainframe environment. The middle chapters provide a roadmap for implementing CI/CD, including details about various tools, steps, and best practices. Case studies are provided to illustrate real-world applications of the concepts presented. The book concludes with a look at future trends, anticipating the trajectory of mainframe CI/CD practices. "Modernizing Mainframes" does not promise a one-size-fits-all solution. Instead, it encourages readers to understand the unique aspects of their own mainframe environments and align them with the best practices in CI/CD. We hope this book serves as a trusted guide in your journey towards a more agile, efficient, and future-ready mainframe environment.