This paper presents a systematic review of Infrastructure as Code (IaC) and GitOps, exploring their transformative roles in cloud automation and governance. IaC, an approach that defines and provisions infrastructure using code, automates cloud infrastructure management, offering significant improvements in consistency, scalability, and agility. GitOps, as an extension of IaC, leverages Git repositories as the single source of truth, enabling seamless continuous delivery and deployment (CI/CD) workflows. This review highlights the synergistic benefits of combining IaC and GitOps, including enhanced operational efficiency, faster scaling, and stronger governance. However, the review also identifies key challenges in their implementation, such as toolchain integration, complexity in large-scale environments, and ensuring governance and security across cloud platforms. Case studies and emerging trends, including AI-powered automation and multi-cloud strategies, are discussed to illustrate real-world applications and future opportunities. The paper concludes by identifying areas for future research, including the development of advanced automation tools, multi-cloud governance frameworks, and improved security compliance mechanisms.