The Shah Mosque (Persian: مسجد شاه) is a mosque located in Isfahan, Iran. It is located on the south side of Naghsh-e Jahan Square. It was built during the Safavid Empire under the order of Abbas the Great.

It is regarded as one of the masterpieces of Persian architecture in the Islamic era. The Royal Mosque is registered, along with the Naghsh-e Jahan Square, as a UNESCO World Heritage Site. Its construction began in 1611.

The mosque is depicted on the reverse of the Iranian 20,000 rials banknote. It was found damaged in 2022.

In 1598, when Shah Abbas decided to move the capital of his Persian empire from the northwestern city of Qazvin to the central city of Isfahan, he initiated what would become one of the greatest programmes in Persian history; the complete remaking of this ancient city. By choosing the central city of Isfahan, fertilized by the Zāyandeh River ("The life-giving river"), lying as an oasis of intense cultivation in the midst of a vast area of arid landscape, he both distanced his capital from any future assaults by Iran's neighboring arch rival, the Ottomans, and at the same time gained more control over the Persian Gulf, which had recently become an important trading route for the Dutch and British East India Companies.

The chief architect of this task of urban planning was Shaykh Bahai (Baha' ad-Din al-`Amili), who focused the programme on two key features of Shah Abbas's master plan: the Chahar Bagh avenue, flanked at either side by all the prominent institutions of the city, such as the residences of all foreign dignitaries, and the Naqsh-e Jahan Square ("Exemplar of the World"). Prior to the Shah's ascent to power, Persia had a decentralized power structure, in which different institutions battled for power, including both the military (the Qizilbash) and governors of the different provinces making up the empire. Shah Abbas wanted to undermine this political structure, and the recreation of Isfahan, as a Grand capital of Persia, was an important step in centralizing the power.

The crown jewel in this project was the Masjed i Shah, which would replace the much older Jameh Mosque in conducting the Friday prayers. To achieve this, the Shah Mosque was constructed not only with vision of grandeur, having the largest dome in the city, but Shaykh Bahai also planned the construction of two religious schools and a winter mosque clamped at either side of it.

The architect of the mosque is Ali Akbar Isfahani. His name appears in an inscription in the mosque above the doorway of the entrance iwan complex. The inscription also mentions that the supervisor of the construction as Muhibb 'Ali Beg Lala who was also a major donor to the mosque. Another architect Badi al-zaman-i Tuni may have been involved in its early design.

Because of the Shah's desire to have the building completed during his lifetime, shortcuts were taken in the construction; for example, the Shah ignored warnings by one of the architects, Abu'l Qāsim, regarding the danger of subsidence in the foundations of the mosque, and he pressed ahead with the construction. The architect proved to be right, as in 1662 the building had to undergo major repairs.

Also, many historians have wondered about the peculiar orientation of The Royal square (The Maidān). Unlike most buildings of importance, this square did not lie in alignment with Mecca, so that when entering the entrance-portal of the mosque, one makes, almost without realising it, the half-right turn, which enables the main court within to face Mecca. Donald Wilber gives the most plausible explanation to this; the vision of Shaykh Bahai was for the mosque to be visible wherever a person was situated in the maydān. Had the axis of the maydān coincided with the axis of Mecca, the dome of the mosque would have been concealed from view by the towering entrance portal leading to it. By creating an angle between them, the two parts of the building, the entrance portal and the dome, are in perfect view for everyone within the square to admire.

The Safavids founded the Shah Mosque as a channel through which they could express themselves with their numerous architectural techniques. The four-iwan format, finalized by the Seljuq dynasty, and inherited by the Safavids, firmly established the courtyard facade of such mosques, with the towering gateways at every side, as more important than the actual building itself.

The distinct feature of any mosque is the minaret, and the Masjed-e Shah has four. Still, in Persian mosques, tall minarets were considered unsuitable for the call to prayer, and they would add an aedicule, known in Persian as a goldast (bouquet) for this particular purpose, which in the Masjed-e Shah stands on top of the west iwan.

The mihrab, a large marble tablet ten feet tall and three feet wide on the southwestern wall, indicated the direction of Mecca. Above it the Shah's men had placed a gold-encrusted cupboard of allow wood. It held two relics: a Quran, said to have been copied by Imam Reza, and the bloodstained robe of Imam Hussain. Although never displayed, the robe was said to have magical powers; lifted on the end of a pike in the battle field, the belief was that it could rout an enemy.

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  View of the mosque from Naqsh-e Jahan Square, showing the difference in orientation between the entrance and the rest of the mosque behind it
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  Entrance iwan of the mosque
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  View from below of the muqarnas over the entrance
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  Panoramic photo of the entrance vestibule leading to the courtyard
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  The main courtyard, with its four-iwan layout
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  The main domed prayer hall
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  View of the mihrab (center) and minbar (right) in the main prayer hall
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  The winter prayer hall, built in hypostyle form

A renaissance in Persian dome building was initiated by the Safavids. The distinct feature of Persian domes, which separates them from those domes created in the Christian world or the Ottoman and Mughal empires, was the colorful tiles, with which they covered the exterior of their domes, as they would on the interior. These domes soon numbered dozens in Isfahan, and the distinct, blue-colored shape would dominate the skyline of the city. Reflecting the light of the Sun, these domes appeared like glittering turquoise gem and could be seen from miles away by travelers following the Silk Road through Persia. Reaching 53 meters in height, the dome of the Masjed-e Shah would become the tallest in the city when it was finished in 1629. It was built as a double-shelled dome, with 14 meters spanning between the two layers, and resting on an octagonal dome chamber.

The Masjed-e Shah was a huge structure, said to contain 18 million bricks and 475,000 tiles, having cost the Shah 60,000 tomans to build. It employed the new haft rangi (seven-colour) style of tile mosaic. In earlier Iranian mosques the tiles had been made of faience mosaic, a slow and expensive process where tiny pieces are cut from monochrome tiles and assembled to create intricate designs. In the haft rangi method, artisans put on all the colors at once, then fired the tile. Cheaper and quicker, the new procedure allowed a wider range of colors to be used, creating richer patterns, sweeter to the eye. According to Jean Chardin, it was the low humidity in the air in Persia that made the colors so much more vivid and the contrasts between the different patterns so much stronger than what could be achieved in Europe, where the colors of tiles turned dull and lost its appearance. Still, most contemporary and modern writers regard the tile work of the Masjed-e Shah as inferior in both quality and beauty compared to those covering the Lotfallah Mosque, the latter often referred to by contemporary Persian historians, such as Iskandar Munshi, as the mosque of great purity and beauty. The architects also employed a great deal of marble, which they gathered from a marble quarry in nearby Ardestan.

The entrance portal of the mosque displays the finest tile decoration in the building. It is entirely executed in tile mosaic in a full palette of seven colors (dark Persian blue, light Turkish blue, white, black, yellow, green and bisquit). A wide inscription band with religious texts written in white thuluth script on a dark blue ground frames the iwan. The tiles in the Masjed-e Shah are predominantly blue, except in the covered halls of the building, which were later revetted in tiles of cooler, yellowy-green shades.

• Chehel Sotoun Palace
• Safavid art
• History of Persian domes

• Mimaran-i Iran by Zohreh Bozorg-nia. 2004. ISBN 964-7483-39-2

• Goudarzi, Masoumeh; Bemanian, Mohammadreza; Leylian, Mohammadreza (2020). "Geometrical analysis of architectural drawnings in the Shah-mosque Isfahan". Curved and Layered Structures. 7 (1): 68–79. Bibcode:2020CLS.....7....7G. doi:10.1515/cls-2020-0007.
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• A Documentary on Isfahan's Royal Mosque (Produced by ARTE)