In a surprise move, Russian President Vladimir Putin has ordered his military to start withdrawing the “main part” of its forces in Syria from Tuesday.
He said the Russian intervention had largely achieved its objectives.
The comments come amid fresh peace talks in Geneva aimed at resolving the five-year Syrian conflict.
Russia is a key ally of Syrian President Bashar al-Assad and his office said in a statement he had agreed to the move.
The pullout was “in accordance with the situation on the ground”, the statement 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.
“I consider the mission set for the Defence Ministry and the armed forces on the whole has been accomplished,” Mr Putin said at a meeting at the Kremlin.
“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.”
Mr Putin also said that Russia’s Hmeimim airbase and its Mediterranean port at Tartus would continue to operate as normal.
He said both must be protected “from land, air and sea”.
Speaking in October last year, Mr Putin said Russia aimed to “stabilise the legitimate authority” of President Assad by intervening and “create conditions for a political compromise”.
Russia has long insisted its bombing campaign only targets terrorist organisations but Western powers have complained the raids hit political opponents of President Assad.
The UN’s envoy to Syria, Staffan de Mistura has meanwhile described the latest peace talks as a “moment of truth”.
He said there was no “plan B” should the talks fail, with the only alternative a return to war.
A cessation of hostilities agreed by most participants in the conflict began late last month – but there have been reports of some violations on all sides.
In the latest fighting, Syrian government forces are reported to have advanced on so-called Islamic State’s (IS) positions near the world heritage site of Palmyra.