More than 1.8 million pilgrims from all over the world have already amassed in and around Mecca for the Hajj.
A spokesman for the Saudi Hajj Ministry said the number was still growing as more pilgrims from inside Saudi Arabia joined.
And authorities have said they expect this year's crowd to approach pre-COVID levels of more than 2 million.
Muslim pilgrims in Mecca have circled the Kaaba, Islam's holiest site, and then converged on a vast tent camp in the nearby desert, officially opening the annual Hajj pilgrimage.
A once in a lifetime experience for many
Egyptian businessman Yehya Al-Ghanam, overwhelmed by his pilgrimage, said he was at a loss to describe his feelings upon arriving at Mina, one of the biggest tent camps in the world outside Mecca, where pilgrims will stay for much of the Hajj.
"Tears will fall from my eyes out of joy and happiness," he said.
"I do not sleep. I have not slept for 15 days, only an hour a day," he said.
The pilgrimage is one of the five pillars of Islam, and all Muslims are required to make the five-day Hajj at least once in their lives if they are physically and financially able to do it.
For pilgrims, it is a deeply moving spiritual experience that absolves sins, brings them closer to God and unites the world's more than 1.8 billion Muslims.
Some pilgrims spend their whole lives saving up for the journey or wait years before getting a permit, which Saudi authorities distribute to countries based on a quota system.
Travel agents offer packages catering to all income levels, and charities assist needy pilgrims.
The biggest crowd since COVID-19
In 2019, more than 2.4 million pilgrims participated in the Hajj.
In 2020, amid worldwide coronavirus lockdowns, Saudi Arabia limited the pilgrimage to a few thousand citizens and local residents.
Last year, just under 900,000 attended as Saudi Arabia allowed limited numbers of pilgrims from abroad.
More than 2 million Muslims will take part in this year's Hajj pilgrimage to the holy city of Mecca in Saudi Arabia, as one of the world's largest religious gatherings returns to full capacity following years of coronavirus restrictions.
Here's a look at the pilgrimage and what it means for Muslims.
Loading...The history behind the Hajj pilgrimage
The pilgrimage draws Muslims from around the world to Mecca, in Saudi Arabia, where they walk in the footsteps of the Prophet Mohammed and retrace the journey of Ibrahim and Ismail, or Abraham and Ishmael as they are known in the Christian and Jewish traditions.
As related in the Koran, Ibrahim is called upon to sacrifice his son Ismail as a test of faith, but God replaced Ismail with a sheep at the last moment.
Ibrahim and Ismail are said to have later built the Kaaba together, a cube-shaped structure covered in a black, gold-embroidered cloth.
In the Christian and Jewish traditions, Abraham nearly sacrifices his other son, Isaac, on Mount Moriah, which is associated with a major holy site in Jerusalem.
The Kaaba was a centre for polytheistic worship among pagan Arabs until the arrival of Islam in the seventh century, when the Prophet Mohammed consecrated the site and inaugurated the Hajj.
Muslims do not worship the Kaaba but view it as their most sacred place and a powerful symbol of unity and monotheism.
No matter where they are in the world, Muslims face toward the Kaaba during their daily prayers.
The Hajj has been held every year since the time of the prophet, even through wars, plagues and other turmoil — including the COVID-19 pandemic.
In the Middle Ages, Muslim rulers organised massive caravans with armed escorts that would depart from Cairo, Damascus and other cities.
It was an arduous journey through deserts where Bedouin tribes carried out raids and demanded tribute.
A notorious Bedouin raid in 1757 wiped out an entire Hajj caravan, killing thousands of pilgrims.
How do Muslims prepare for the Hajj?
Pilgrims first make their way by foot or by bus to Mina, a valley located 8 kilometres south-east of the city of Mecca.
The faithful set up in their tents, resting in the rows of cubicles and praying together to prepare for the coming rituals.
Pilgrims then begin the ritual by entering a state of spiritual purity known as "ihram".
Women forgo make-up and perfume, and they cover their hair, while men change into seamless terrycloth robes.
The garments cannot contain any stitching, a rule intended to promote unity among rich and poor.
Pilgrims are forbidden from cutting their hair, trimming their nails or engaging in sexual intercourse while in the state of ihram.
They are not supposed to argue or fight, but the heat, crowds and difficulty of the journey inevitably test people's patience.
Many Muslims also visit Medina, where the Prophet Mohammed is buried and where he built the first mosque, before heading to Mecca.
What happens during the Hajj?
The Hajj begins with Muslims circling the Kaaba in Mecca counter-clockwise seven times while reciting prayers.
Then they walk between two hills in a re-enactment of Hagar's search for water for her son, Ismail, a story that occurs in different forms in Muslim, Christian and Jewish traditions.
All of this takes place inside Mecca's Grand Mosque — the world's largest — which encompasses the Kaaba and the two hills.
The next day, pilgrims head to Mount Arafat, east of Mecca, where the Prophet Mohammed delivered his final sermon.
Here, they stand in prayer throughout the day, asking God for forgiveness of their sins in what many view as the spiritual high point of the pilgrimage.
Around sunset, pilgrims walk or take buses to an area called Muzdalifa, west of Arafat.
They pick up pebbles to use the next day in a symbolic stoning of the devil in the valley of Mina, where Muslims believe Ibrahim was tempted to ignore God's command to sacrifice his son.
The pilgrims stay for several nights in Mina in one of the largest tent camps in the world.
How does the ritual end?
The pilgrimage ends with a final circling of the Kaaba and further casting of stones at Mina.
Men often shave their heads and women clip a lock of hair, signalling renewal.
Many will assume the title of "hajj" or "hajja" — a great honour, particularly in more traditional communities.
ABC/ AP