With the increasing importance of sustainability on a global scale, it has become evident that stakeholders attach importance not only to the financial performance of businesses but also to their environmental, social, and governance activities. In this context, sustainability reporting has become an important reporting tool that enables businesses to present their non-financial information in a transparent, comparable, and accountable manner. Presenting information regarding businesses’ environmental impacts, social responsibility activities, and governance practices contributes to strengthening the understanding of sustainable corporate governance. However, increasing expectations regarding the reliability and accuracy of the information included in sustainability reports have made it necessary for these reports to undergo independent assurance auditing. In this study, the concepts of sustainability, corporate sustainability, sustainability reporting, and assurance auditing are discussed within a conceptual framework. The historical development, scope, benefits, and national and international reporting standards of sustainability reporting are examined. In addition, assurance auditing practices aimed at increasing the reliability of sustainability reports, assurance standards, and the problems encountered in this process are evaluated. Furthermore, current regulations regarding sustainability reporting and assurance auditing in Türkiye, as well as practices carried out within the scope of the Türkiye Sustainability Reporting Standards, are discussed. As a result, sustainability reporting and assurance auditing practices are considered to make significant contributions to increasing corporate transparency, strengthening stakeholder confidence, ensuring the reliability of reported information, and improving the understanding of sustainable corporate governance.