The event, which falls on the 18th of Dhul-Hajjah on the lunar calendar, is one of the most significant days for Shia Muslims worldwide.
In the capital Tehran, the streets are decorated with flags and decorative elements as part of the celebrations.
An event is organized in the capital Tehran to host a 10-km-long celebration march, which has gathered over 3 million people in previous years, hailed as the world’s largest celebration event of its kind.
The participants are treated with food and drinks and musical performances.
Large celebrations are also held on the streets in other cities on the occasion.
Imam Ali was the Prophet’s cousin and his son-in-law and is known as the first man who embraced the Prophet’s call for Islam.