The Hajj (pilgrimage) is an annual Islamic pilgrimage to Mecca, and a mandatory religious duty for Muslims that must be carried out at least once in their lifetime by all adult male Muslims who are physically and financially capable of undertaking the journey.
It is one of the five pillars of Islam, alongside Belief, Prayer, Charity and Fasting.
The gathering during Hajj is considered the largest annual gathering of people in the world.