This thesis is a comparative study of the doctrine of utmost good faith in the realm of marine insurance law under three different laws. These are the English Marine Insurance Act of 1906, Egyptian Marine Trade Law of 1990 and Saudi Arabian Commercial Court Law of 1931. The thesis explores and investigates the bundle of rights and liabilities which are generated by the imposition of the doctrine on the assured and his agents before and after the inception of the contract including the time at which a claim for loss is presented. Its central goals will basically be to make a comparative and detailed analysis of the current application of the doctrine and to take advantage of its results to develop and promote the Saudi Arabian doctrine. In particular, the thesis will concentrate on how the doctrine is currently applied, what its aspects of strength, weakness and limitation are and what the consequences of its violation are? These themes will be carried out through the examination of the key concepts upon which the application of the doctrine is based, namely the duty of disclosure, the duty to refrain from making misrepresentations and the concepts of materiality and actual inducement. Also, due to the fact that the doctrine has different application and remedies after the conclusion of the contract, the thesis intends to devote a separate chapter for its discussion and examination at this stage. The importance of this thesis appears, besides other factors, in its novelty as being the first thesis to subject the Saudi Arabian and Egyptian doctrines of utmost good faith in the realm of marine insurance to an extensive, comparative and academic research. Therefore, it is hoped that it will make a pioneering contribution to the field of legal studies and lead to a better understanding of the application of the doctrine not only under the Saudi Arabian and Egyptian laws, but also under the English.