The Russian President, Vladimir Putin, has ordered his military to start withdrawing the "main part" of its forces from Syria, saying the intervention had largely achieved its objectives.
Mr Putin said the pull-out should start later today.
"I consider the mission set for the Defence Ministry and the armed forces on the whole has been accomplished.
"I am therefore ordering the Defence Ministry to begin the withdrawal of the main part of our military force from the Syrian Arab Republic from tomorrow (Russian time)," Mr Putin said at the Kremlin meeting.
Mr Putin said that Russia's Hmeimim airbase and its Mediterranean port at Tartus would continue to operate as normal.
Both must be protected "from land, air and sea", he said.
The announcement comes as fresh peace talks are about to begin in Geneva, aimed at resolving the five-year Syrian conflict. Mr Putin has said Russia would intensify its role in the peace process to end the conflict in Syria.
A Kremlin spokesperson said Mr Putin telephoned the Syrian President, Bashar al-Assad, to inform him of the decision.
Syria and Russia had agreed to reduce the presence of Russia's air force in Syria after it helped the Syrian army make military gains, the Syrian presidency said in a statement.
It said it was in line with "the continuation of the cessation of hostilities and in accordance with the situation on the ground".
Russia also pledged to continue its support for Syria in "combating terrorism", the Syrian presidency said.
Russia's entry into the Syrian civil war in September 2015 tipped the balance in favour of the Syrian government, allowing it to recapture territory from rebels.