The journey is seen as one of the five pillars of Islam, central to the faith.
Pilgrims spend five days praying both in Mecca and the surrounding desert.
It is a spiritual pilgrimage that every adult Muslim must perform at least once in their lives if they can afford it and are physically able.
In order to be closer to God, they wear simple clothes, aren't allowed to argue and perform rituals such as throwing stones at pillars to symbolise rejecting evil.
Every year, millions of Muslims travel from around the world to Saudi Arabia to complete the Hajj pilgrimage in the holy city of Mecca.