Many Greeks object to Macedonia because their country has a region of the same name and argue the former Yugoslav Republic’s use of the term, along with contentious articles in its constitution, imply territorial claims over Greek land.
The two countries have agreed to step up negotiations, mediated by the United Nations, this year to settle the dispute, which has frustrated the aspirations of Greece’s small northern neighbour to join NATO and the European Union.
But protesters turned Athens into a sea of people waving blue and white Greek flags in what locals said was the largest gathering in decades.
A giant Greek flag was hoisted over the demonstration by a crane while demonstrators held banners reading “Hands off Macedonia!” and chanted the national anthem.
World-famous Zorba The Greek composer Mikis Theodorakis, 92, was among those addressing the crowds.
He told the rally: “Macedonia was, is and will forever be Greek.
“If a government considers signing on behalf of our country there is no doubt it must first ask the Greek people.
“If we give in, we are leaving the doors wide open for a tragic historical lie to come through and stay forever.”
The case evokes strong emotions among Greeks who consider Macedonia, the ancient kingdom ruled by Alexander the Great, to be an integral part of their homeland and heritage.
Talks also reopened at a sensitive time for a country struggling to emerge from its worst debt crisis in decades and to regain sovereignty over economic policy-making after years of austerity mandated by international lenders.
Talks between the two countries have made little headway since the Balkan state broke away from Yugoslavia in 1991.
Due to Greece’s objections, Macedonia was admitted to the United Nations with the provisional name “The Former Yugoslav Republic of Macedonia” in 1993, which remains its official title in international organisations.
A majority of countries in the world refer to it simply as Macedonia.
Greece’s leftist-led government has proposed a compound name, with a geographical qualifier, which would be the only name that could be used for the country.
But opinion polls show a majority of Greeks oppose the use of “Macedonia” in any solution.
Foreign Minister Nikos Kotzias said Greece was preparing proposals which would be the basis of negotiations for a settlement with its neighbouring country.