Some pilgrims have donned clothing featuring the names and flags of their countries. "Hajj 2020 -- Chad" was written on the back of the white robes of one group.
Hosting the hajj is a matter of prestige and a powerful source of political legitimacy for Saudi Arabia's rulers.
Costing at least $5,000 per person, the hajj is also a money-spinner for the world's biggest oil exporter, which is trying to diversify its economy.
In normal years, the pilgrimage brings in billions of dollars.
These days it represents a chance to showcase the kingdom's ongoing social transformation, despite persistent complaints about human rights abuses and limits on personal freedoms.
Saudi Arabia now allows women to attend the hajj unaccompanied by male relatives, a requirement that was dropped last year.