Legitimate defense is an inherent right recognized by divine law from time immemorial, and human nature is based on the sense of survival that arises in the soul of the defender. This study aims to highlight all elements of the subject of legitimate defense in a scientific work, as well as it aims to enable the legal community with all of its components, not only at the level of university studies, to take cognizance of the details of the subject in both theoretical and practical terms. This study relies on descriptive, analytic, and comparative method; and it is divided into two chapters, the first defined legitimate defense, as for the second, discussed provisions of legitimate defense. The study has reached a number of results and recommendations; one of the most significant results are that the penal codes are not collaborating with Fiqh in determining the nature of legitimate defense and if it is considered a right or duty or a license. The study finds also that the idea of legitimate defense in Omani Penal Code is of dual-use nature. The study also reached a set of recommendations of which the most prominent is to be explicitly stipulated that it is permissible to defend by mechanical defense tools and regulate its provisions. It also stipulates that the defense against assault on legal persons is similar to other comparative laws.