The organizers of the rally, called "Macedonia is Greece," said that the event was non-partisan and not supported by any political party.
Greek media reported that extraordinary security measures would be taken during the event, including stationing of 19,000 policemen.
A similar rally took place in January and was attended by over 100,000 people.
Greece and Macedonia have been involved in a dispute over the name of the Republic of Macedonia since the latter declared independence from Yugoslavia in 1991. Athens has been claiming that Skopje might have territorial claims over Greece’s own region of the same name, insisting on another name for the neighboring country.
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.
