Saveh Grand Mosque, as one of the most significant historical and religious monuments in Iran, has a distinguished position in the formation of the physical, cultural and spiritual identity of Saveh city and has always been known as one of the most important elements of the spatial organization of this city. The present study aims to investigate the position of Saveh Grand Mosque in representing the Islamic and cultural identity of the city, the process of its architectural evolution in different historical periods and the role of this building in organizing the urban structure. The research method is based on field studies, a review of library resources and a systematic analysis of historical documents, records and inscriptions.The research findings show that the initial core of the mosque dates back to the early Islamic centuries, especially the second century AH, and was formed based on the pattern of the Shabestani and pillared mosques, similar to the historical Damghan Mosque. During the Seljuk period, with the construction of the brick dome and minaret dated 504 AH, the physical structure of the mosque was transformed from a horizontal spatial organization to a concentrated and vertical combination. Further, architectural interventions during the Ilkhanid and Safavid periods, through the construction of high porches and the implementation of extensive renovations, led to the consolidation of the current spatial organization of the building. Examination of the building layers and decorative elements, including stucco moldings, tiling, and valuable inscriptions, shows that the Saveh Grand Mosque was not merely a religious building.Rather than standing in isolation, it has served as the city's central core, playing a pivotal role in forging spatial and functional connections among key elements such as the bazaar, caravanserais, and other urban spaces. Consequently, a precise understanding of the monument's evolution—beyond revealing the historical and cultural identity of Saveh—provides a scientifically grounded basis for formulating strategies regarding the conservation, restoration, and management of cultural heritage, thereby presenting the Jameh Mosque as a living, legible testament to the city's history and identity at the heart of Saveh.