The annual pilgrimage is expected to draw more than two million pilgrims this year.
An estimated one million Muslims have already arrived in the holy city.
The pictures show different aspects of the pilgrimage which involves circling Kaaba, Islam’s holiest and most sacred site.
Each person must walk counter-clockwise seven times around the Ka’ba in Masjid Al-Haram.
The rites performed at Hajj were established by the Prophet Muhammad but are based on the Qur’an.
They can be traced back to the Prophet Ibrahim, also referred to in English as Abraham.
In 2010 three million Muslims attended Hajj, it was the highest number recorded so far and the pilgrimage became the 10th biggest gathering in human history.
Hajj takes place from Sunday, August 19 to Friday, August 24.
The Day of Arafat is an Islamic holiday which falls on the 9th day of Dhul al-Hijah of the lunar Islamic Calendar.
It is the second day of the Hajj pilgrimage and begins in the evening of Monday, August 20 and ends in the evening of Tuesday, August 21.
On the Day of Arafat millions of pilgrims set out for the plains of Arafat after sunrise to attend Mount Arafat, where the Prophet Mohammad gave his last sermon.
Pictures from Mecca show pilgrims taking selfies in the lead up to Hajj.
And Saudi security officers checking monitors of the holy city as millions flood into the complex.
Muslims stand shoulder to shoulder as they pray in unison all facing towards Kaaba.
Hajj is one of the fiver pillars of Islam, alongside faith, prayer, charity and fasting.
It is mandatory for Muslim adults to go on Hajj at least once in their lifetime.
The pilgrimage must take place during the month of Dhul al Hijja, the last month of the Islamic calendar and the rites of Hajj are performed from the 8th to the 12th at Dhul al Hijjah.
The event is linked to Islamic prophet Muhammad, whose journey from Medina to Mecca in the 7th century became the first Hajj.
However it can be built back even further to the time of Ibrahim who built the Kaaba and invited people to carry out a pilgrimage there.