This study aims to compare the spatial features of mosques in Turkey and Indonesia, both predominantly Muslim countries. The introduction provides a general definition of religion and highlights the significance of religious structures. It explains that religion is a belief system and emphasizes the importance of religious structures for societies. The formation and development of religious buildings often rely on sacred texts, rituals, moral principles, and societal rules. Mosques are significant religious spaces where Muslims gather for collective worship. They contribute significantly to areas such as culture, architecture, and art. However, this study scrutinizes and reviews the differences and similarities in the design, implementation, and use of mosques in Turkey and Indonesia, taking into account academic studies on the subject. In both countries, mosques are built in two different styles: Classical and modern. The study examines well-known mosques in Turkey, including the Sultan Ahmet Mosque and the Suleymaniye Mosque (classical style) and the Şakirin Mosque and the Sancaklar Mosque (modern style). The study includes classical style mosques such as the Al Mahsun Grand Mosque and the Baiturrahman Grand Mosque, as well as modern style mosques like the Istiqlal Mosque and the Babuttaqwa Utama Mosque in Indonesia. These mosques were chosen as prominent examples based on the time periods they were built, their purposes of construction, their current uses, and their impact on their respective contexts. Although there have been numerous academic studies on mosque architecture in Turkey and Indonesia, there is a lack of literature that comparatively examines mosque architecture formation in the context of cultural and spatial differences between these two cultures. This gap highlights the importance of the current study.