Thousands have descended at Syntagma Square in the center of the Greek capital for the rally on Macedonia.
Organizers expect hundreds of thousands to arrive from every corner of Greece.
The Greek Reporter is covering the rally live. You can follow developments here.
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.
Rally spokesman Michalis Patsikas told reporters that “it will be majestic. This has never happened before.”
The rally is scheduled to start at 02:00 p.m. local time (12:00 GMT) at 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.
The keynote speaker at the rally will be the famous composer Mikis Theodorakis.