Application of Polycentric Urban Regions concept in Iran’s Metropolitan Areas Theoretical Origin: Looking at the research on polycentric urban regions, two approaches can be distinguished: The first approach: looking upon the similarity of a polycentric urban region with geographic theories centered around polycentric cities or some others as attitudes including garden cities, urban networks or spatial approach of decentralization in the form of the French idea of métropoles d’équilibre The second approach: specific concept of polycentric urban region as a notion which has been observed in the efforts made by member countries of European Union in the last two decades As it is shown in the chart of applied research for this subject, the second approach is rapidly growing in the countries on a variety of scales. This paper, by an overview on the records and definition of this concept, is trying to explain the cons, pros and some evaluations about Polycentric urban region. Furthermore, with an overview of the regional plans in Iran, the capability of using this concept was assessed at various scales and simultaneously some contextual-structural considerations and differentiations for usability of this concept were extracted. Now, due to the absence of a metropolis or large city, there is no particular pattern or approach for the notion of polycentric urban region. However, it seems that in the regional planning system of Iran, the polycentric urban region concept can be applied to promotion of regions’ urban system and their spatial development strategies. Moreover, this concept is applied in synergy with wide arrays of objectives and spatial development strategies in Iran including decentralization decrease in regional disparities and enhancing the small and mid-sized towns. One of the first assumptions in this regard is that by formalizing Polycentric Urban Region, the new dimensions of synergy and complimentary will  be emerged. Besides, increased interactions and connections between these cities led to internal coherence and external competitiveness. As an illustration, the well-known case of an urban area which is located in the north of Iran (central urban region of Mazandaran province) can take the advantage of similar financial and legal benefits (according to the regulations) which are currently assigned to the metropolitan areas. Major literature around polycentric urban region are focused on the most urbanized and compression regions in the Western Europe. It seems that the conditions surrounding the origin of this notion have had beneficial role in the development of polycentric idea. Owing to this fact, there have been some intrinsic differentiations between the prominent classical instances of polycentric urban regions (in Western Europe) and existing conditions in Iran which will be discussed below: - Strong communication infrastructure network between cities together with direct and immediate connections between the cities of the region: this issue has been considered somewhat self-evident, but in the case of Iran; it needs to be more emphasized. - Based on the form, most classical instances of polycentric urban region have taken the advantage of nonlinear form with intermediary matrix communications between settlements and diverse and high-quality access to destinations. - Locating all well-known reference instances of polycentric urban regions in plains and flat topographic terrains: while according to the position of cities in Iran, most of which are typically located in mountainside, this difference can be effective in the application of this concept. - In the index instances, targeting has been based on competitiveness and globalization in formation and development of polycentric urban region (PUR) but at least in the medium term, it cannot be included the goal of developing PUR’s in Iran. - Federal or relatively decentralized governance system provides a more favorable context for emerging and formation of such a regional framework. Propositions: 1- It is suggested that the polycentric urban region is included on the agenda of High Council of Urbanization and Architecture of Iran  2- The polycentric urban regions distinctively shall be specified in the system of Iran spatial planning for facilitating regional planning objectives such as development and competitiveness of small and mid-sized cities, decentralization of urban system and reduction of migration process towards metropolitan areas.