After a day of marathon talks in Geneva, US Secretary of State John Kerry and Russia's Foreign Minister Sergei Lavrov announced the truce, which is set to come into force on Monday (local time), the first day of the Muslim holiday of Eid.
Mr Kerry said he believed the plan would lead to talks to "stop the conflict" which has raged for more than five years, killing more than 290,000 people and displacing millions.
He called on "every Syrian stakeholder" to support the plan to "bring this catastrophic conflict to the quickest possible end through a political process".
