Thousands have descended from every corner of Greece at Syntagma Square in the center of Athens for the rally on Macedonia.
Rally spokesman Michalis Patsikas told reporters that “it will be majestic. This has never happened before.”
The keynote speaker at the rally will be the famous composer Mikis Theodorakis.
Hundreds of buses were chartered to bring protesters from across the country to the Greek capital for Sunday’s rally. More were arriving on ferries from the islands.
The rally is scheduled to start at 02:00 p.m. local time (12:00 GMT) at the Syntagma square in central Athens and expected to last for two hours.
It is being organized and funded by Greek diaspora groups, backed by retired officer associations, Greek Macedonian cultural unions, church groups, and others.
Watch our live coverage from Syntagma: