Objective: Purpose of this study is to review the definitional framework of rare books and to study the historical evolution of special collections in the world and in Iran. Methodology: Descriptive method with inductive approach has been used. First, it reviewed the existing definitions of rare books and their shortcomings to finally reach a comprehensive definition; then the historical course of special collections in the world was analyzed and the history and libraries with special collections in Iran were reviewed. The sources used in this research have been collected using documentary and library methods. Findings: Rare books have a definition beyond the old books and the process of transferring information in them does not only include content data. In the second part, four stages were achieved regarding the evolution of special collections in the world (Identification and segregation of rare books; The evolution of rare books in academic libraries; The evolution of rare books and special collections with the opening of these sections in university libraries; Forming a professional organization (ACRL) to meet educational and communication needs), as well as the differences in approaches to special collections in different societies and cultures and the differences between blacks and whites due to differences of concern throughout history. According to experts, in terms of historical position by global definition, we are now in the fourth stage. By reviewing special collections in Iran, the first library with special collections was the library of Vank Church in Isfahan, and in total, 21 libraries with special collections were found in Iran. Conclusion: Contrary to popular belief, the definition of the term "rare book", which is an important resource in special collections, can vary based on the missions and goals of libraries and their overall strategies, and in general, may not be outside the strategic framework of libraries. Books can be considered potentially scarce and the basis for identifying rare books is largely dependent on the mission of the collections and cannot be evaluated independently. Also, the history of special collections in Iran, unlike the world, does not have a clear course. The stages of its evolution are not clearly defined and the information available in this regard is related to the libraries that have these collections, and the initial purposes of their formation have been largely distorted. This issue will require serious attention to the field of research, and the elimination of existing shortcomings by researchers with different orientations. [ABSTRACT FROM AUTHOR]