Greece says it has recovered hundreds of looted artefacts, including a 2nd-Century bronze statue of Alexander the Great.
The trove was recovered after a legal battle with the company of a British antiquities dealer, officials said.
Robin Symes had amassed thousands of pieces as part of a network of illegal traders.
For years, Greece has been fighting to recover looted artefacts from museums and private collections world-wide.
The announcement that 351 objects from Symes's collection were being repatriated after a 17-year legal battle was made by Greek Culture Minister Lina Mendoni on Friday.
Ms Mendoni did not say if the artefacts were linked to the discovery by Italian and Swiss police in 2016 of a haul of archaeological treasures said to have been stored by Symes at the Geneva freeport in Switzerland.
Arguably the most high-profile artworks in the debate about whether museums should return items to their countries of origin are the Parthenon Sculptures.
They were removed from the Parthenon temple in Athens in the early 19th Century by the British soldier and diplomat, Lord Elgin. The sculptures were then bought by the British government in 1816 and placed in the British Museum.
Talks about their return are said to be advancing.
In March, the Vatican returned three fragments of Athens' Parthenon temple it had kept for centuries.