The ceasefire announced Tuesday is a major step toward ending nearly 14 months of fighting sparked by the ongoing war in Gaza between Israel and Hamas.
Israel has said it will attack if Hezbollah breaks the ceasefire agreement.
The ceasefire calls for an initial two-month halt to fighting and requires Hezbollah to end its armed presence in southern Lebanon, while Israeli troops are to return to their side of the border. An international panel led by the United States will monitor compliance.
The ceasefire began at 4 a.m. Wednesday, a day after Israel carried out its most intense wave of airstrikes in Beirut since the start of the conflict that in recent weeks turned into all-out war.