The Shrine of Abu Lu'lu'a (Persian: بقعه ابولولو), also known as the Shrine of Bābā Shujāʿ al-Dīn (بقعه بابا شجاع الدين) is a mausoleum built over what is popularly believed to be the final resting place of Abu Lu'lu'a Firuz, a Persian slave who assassinated the second Islamic caliph Umar ibn al-Khattab in 644.

The structure dates back to the Mongol era, and is located in Kashan (Isfahan Province, Iran). Traditionally, it was the central location of a yearly festival celebrating Abu Lu'lu'a, called Omar Koshan ("the Killing of Umar").

The building was closed in 2007 by the Iranian government, due to pressure from the International Union of Muslim Scholars.

The original structure was built before the Safavid period (1501–1736), at some time during the Mongol era (13th–15th century). However, the building's dome and iwan date from the Safavid period or later.

The historical Abu Lu'lu'a died in Medina (the capital of the early caliphate, situated in the Arabian Peninsula) shortly after his assassination of Umar ibn al-Khattab in 644 CE. At some later time, legends arose according to which Abu Lu'lu'a was saved from his pursuers by Ali ibn Abi Talib (the cousin and son-in-law of the prophet Muhammad, who is also revered by Shi'ite Muslims as the first Imam). According to these stories, Ali instantaneously transported Abu Lu'lu'a by means of a special prayer to Kashan, where he married and lived out the rest of his life.

During the 16th-century Safavid conversion of Iran to Shia Islam, a festival started to be celebrated in honor of Abu Lu'lu'a, commemorating his assassination of Umar. Named Omar Koshan (lit. 'the killing of Umar'), it was originally held around Abu Lu'lu'a's sanctuary in Kashan, each year at the anniversary of Umar's death (26 Dhu al-Hijja of the Islamic year). Later it also started to be celebrated elsewhere in Iran, sometimes on 9 Rabi' al-Awwal rather than on 26 Dhu al-Hijja. The festival celebrated Abu Lu'lu'a, nicknamed for the occasion Bābā Shujāʿ al-Dīn (lit. 'Father Courageous of the Faith'), as a national hero who had defended the religion by killing the oppressive caliph.

Due to political sensitivities, from the Qajar period (1789–1925) onward the festival gradually stopped being celebrated in the major cities of Iran, until it was eventually banned officially by the Islamic Republic of Iran in 1979. Nevertheless, the festival itself is still celebrated in Iran, though often secretly and indoors rather than outdoors. It is now held on the 9th day of the month of Rabi' Al-Awwal of the Islamic year, lasting until the 27th of the same month.

In recent years, controversy was caused when al-Azhar University demanded the Iranian government demolish Abu Lu'lu'a's shrine because the shrine was considered to be "offensive and un-Islamic" by mainstream Sunni scholars. The issue caused the cancellation of diplomatic relations between the university and the Iranian government. Due to this Sunni pressure, which also included an intervention by the International Union for Muslim Scholars, the Iranian government shut down the shrine in 2007.

• List of historical structures in Isfahan Province
• List of mausoleums in Iran

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