More than 100,000 Greeks have protested in the city of Thessaloniki to demand the country of Macedonia stops using the name.
The rally is part of a 27-year disagreement between the Greek province of Macedonia, of which Thessaloniki is the capital, and the country of Macedonia.
In 1991 the country, neighbouring the province, became known as The Former Yugoslav Republic of Macedonia – or FYROM – after declaring independence.
Greece has opposed the name ever since, saying its region has been named Macedonia since Alexander the Great – also known as Alexander III of Macedon – ruled from 336 BC.
Athens argues the name Macedonia suggests Skopje has territorial claims to the northern Greece region.
Rally organisers claimed 400,000 people took part in Sunday’s protest, while police estimated the crowd at 100,000.
The rally was poignantly staged in front of the statue of Alexander the Great.
In 2004, then US President George W Bush caused anger in Greece when he recognised the FYROM as Macedonia.
Until then all NATO allies, apart from Turkey, had joined Greece in refusing to recognise the Balkan state’s new name.
Central Macedonia, in Greece, is the country’s most popular tourist destination.