Syrian government forces – backed by heavy Russian air support – are said to have driven ISIL militants out of Palmyra.
The army is describing it as a mortal blow.
The so-called Islamic State seized the city last year and set about destroying its ancient temples.
Syrian president Bashar al-Assad says Palmyra’s recapture shows the “success” of the army’s strategy, according to reports.
It opens up a huge expanse of desert leading to the militant strongholds of Raqqa and Deir al-Zor.
During a visit to Jordan, UN chief Ban Ki-moon expressed his relief that Palmyra is out of ISIL hands.
“We are encouraged and fortunate that Syrian government forces have been to retrieve or defeat ISIS from Palmyra and is now able to preserve and protect these human common asset – cultural asset,” said Ban.
It is one of the biggest blows for ISIL, which declared a caliphate in 2014 across large parts of Syria and Iraq.
The army says the city will now be used as a “launchpad” to expand military operations against the militants.