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 dynasty under the order of Shah Abbas I of Persia. It was also known as the Imam Mosque after the Iranian Revolution.

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, and its splendour is mainly due to the beauty of its seven-colour mosaic tiles and calligraphic inscriptions.

The mosque is depicted on the reverse of the Iranian 20,000 rials banknote.