Seyyed Mosque (Persian: مسجد سید) is a historic 19th-century mosque located in Isfahan, Iran. It was built during the rule of the Qajar dynasty, by the Shi'ite cleric Mohammad Bagher Shafti, one of the first clerics to receive the rank of Hujjatul Islam. The mosque itself is active, but its construction is not entirely complete.

Construction of the mosque started in the year 1825. It was built over an older plot of land planned for a mosque that was formerly owned by Safavid ruler, Soltan Hoseyn, but a mosque could not be built there until the Qajar era due to the invasion of Nader Shah Afshar and Hotaks. After the death of Mohammad Bagher Shafti, only the tiling of the southern part of the mosque had been completed. He was buried in the northeastern section of the mosque as well. The grandson of the cleric and subsequent descendants assisted in continuing the construction of the mosque. Inscriptions date the whole construction process to be around 130 years, divided into four stages. In the modern age, the mosque was damaged during the Iran-Iraq war. It was then neglected due to disputes amongst the remaining family of Bagher Shafti. In 2023, restoration and renovation works were planned to be carried out.

The plan and base of the Seyyed Mosque is generally a rectangular shape. The mosque has two domes, the smaller, northeastern one over the mausoleum of Mohammad Bagher Shafti and his family. The mosque has four main iwans leading to it, as well as a lot of corridors within the structure. The exterior of the mosque is enhanced with Qajar-era decorative tiling.

The mosque does not have a minaret. Instead, it has a tall clock tower, located behind one of the iwans. In general, the architecture of the mosque, especially the window design is student-friendly, so that it could be used as a school or madrasah in the 19th century as well.

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  Seyyed Mosque at night
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  A closeup of one of the entrances of Seyyed Mosque
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  Qajar-era decorative tilework
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  The tomb of Bagher Shafti, enclosed by a metal zarih
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  One of the musalla rooms in the mosque, with a fine mihrab preserved

• List of mosques in Iran
• List of historical structures in Isfahan