The Syrian government and rebel groups have agreed a nationwide ceasefire from midnight local time (22:00 GMT) on Thursday, followed by peace talks.
The deal was announced by Russian President Vladimir Putin and confirmed by the Turkish foreign ministry.
Russia and Turkey, which back opposing sides, will act as guarantors.
The rebel High Negotiations Committee (HNC), seen by the UN as the main opposition group, confirmed the deal, which excludes jihadist groups.
The Syrian army said in a statement that so-called Islamic State (IS) and Jabhat Fateh al-Sham (formerly the Nusra Front) “and the groups affiliated to them” were not part of the agreement.