Coordinates: 36°17′16.94″N 59°36′56.66″E / 36.2880389°N 59.6157389°E / 36.2880389; 59.6157389

Imām Reza shrine (Persian: حرم امام رضا‎) in Mashhad, Iran is a complex which contains the mausoleum of Imam Reza, the eighth Imām of Twelver Shi'ites. It is the largest mosque in the world by dimension and the second largest in capacity. Also contained within the complex include: the Goharshad Mosque, a museum, a library, four seminaries, a cemetery, the Razavi University of Islamic Sciences, a dining hall for pilgrims, vast prayer halls, and other buildings.

This complex is the center of tourism in Iran. The shrine itself covers an area of 267,079m² while the seven courtyards which surround it cover an area of 331,578m² - totaling 598,657 m² (6,443,890 sq ft).

In 818 Imam Reza was murdered by Al-Ma'mun and was buried beside the grave of Harun. After this event this place was called as Mashhad al-Rida (the place of martyrdom of Ali al-Rida). Shias and sunnis started visiting there for pilgrimage of his grave. By the end of the 9th century a dome was built on the grave and many buildings and Bazaars sprang up around it. During more than a millennium it has been devastated and reconstructed several times.