This study addressed the issue of Sharia's supervision in Islamic banks and its role and challenges in Islamic banks in general and in Islamic banks in the Sultanate of Oman in particular through the statement of Omani legislation and laws in this field and the practical reality in some Islamic banks in the Sultanate of Oman like Nizwa Islamic Bank and Meethaq Islamic Banking. This study's methodology required the division of the thesis into a preliminary and two semesters. The introductory chapter dealt with the concept of Sharia's supervision, its names, importance, legitimacy, adaptability, and its components and controls. The first chapter discussed the role of the Sharia's Supervisory Boards in Islamic Banks, and the role of the follow-up and forensic auditing units, which represent the internal body supporting the Sharia's Supervisory Boards in Islamic Banks, as well as the role of the Supreme Supervisory Authority in the Sultanate Chapter II discussed the most important challenges facing the supervision of Sharia, and the proposed solutions, and the suspicions and shortcomings contained in the supervision of the legitimacy, and also dealt with the most important guarantees of the success of Sharia's supervision in Islamic banks. The study concludes with a statement of the results of the research, the most important of which is: The existence of the Sharia's Supervisory Board in Islamic banks is one of the most fundamental differences between them and conventional banks. The main role of the Sharia's Supervisory Boards is to establish controls for the transactions of these banks and to verify their compliance with the provisions of Islamic Sharia. There are many challenges that hinder the work of the supervision legitimacy such as professional scarcity, dependency, and the tracking of licenses and other than to find effective solutions to them.