The internal audit of capital projects-especially in sectors as critical as oil, gas, electricity, and infrastructure-has become a matter of strategic importance. In nations like Iran, where capital-intensive projects are often managed by public entities and financed through state budgets or international arrangements, ensuring transparency, accountability, and efficiency is more essential than ever. This book, Internal Auditing in Energy Sector Contracts: Oil, Gas and Power Projects, is the product of extensive research, field experience, and collaboration with industry professionals. It aims to provide auditors, engineers, project managers, and public sector leaders with a structured framework for understanding and implementing effective internal audit practices in complex project environments. Drawing on international standards such as those of the Institute of Internal Auditors (IIA), COSO, and ISO, as well as Iranian regulations, this work bridges the gap between global best practices and local realities.