One of the lesserـknown institutions in our law is the institution of "priority right of gaining ownership", which is very important to know its nature. Determining whether any authorityis a right or not has several legal implications. The present research aims to provide a general theory about the priority right of gaining ownership while stating the scattered rulings in the laws and analyzing them about the mentioned institution. In this article, firstly, the special nature of the priority right of gaining ownership and then its elements are analyzed, and finally, the possibility of voluntary and involuntary transfer (inheritance) is examined. The result of the research is that we consider the priority right of gaining ownershipas a kind of right that is created under the protection of the law, and its owner creates the legal effect (gaining ownership) simply by declaring his will, and others must declare and express the will of the owner in front of it. To comply and obey. The privilege of this authority (sovereignty) over the permission (or the general freedom and ability) is that it is dedicated for a specific person and this person has priority in using it.