Briefing the UN Security Council via video link from the Tel Aviv airport, Ban said: "I warmly welcome today's ceasefire announcement. I commend the parties for stepping back from the brink and I commend President Morsi of Egypt for his exceptional leadership."
The secretary-general was visiting the Middle East region to push for an early end to the week-long hostilities, Xinhua reported.
The Israel-Hamas conflict reportedly killed more than 140 Palestinians and at least five Israelis, and left about 1,000 others injured on both sides.
"Our focus now must be on ensuring the ceasefire holds and that all those in need in Gaza - and there are many - receive the humanitarian assistance they need," Ban said.
"It's a huge relief for the people of Gaza and Israel, and for the international community, that the violence is stopping."
Leaders of the EU hailed the ceasefire soon after it was proclaimed.
"We welcome wholeheartedly the cease-fire that has just been proclaimed in Gaza and that was being strongly called for by the European Union and the international community," said a statement jointly issued by the European Council President Herman Van Rompuy and the European Commission President Jose Manuel Barroso.
Head of the Hamas-run government in the Gaza Strip, Ismail Haneya, in a statement emailed to the media, said he was proud of the Palestinian people's steadfastness and their armed resistance.
"We congratulate our people for this victory, as the Palestinian people and their resistance proved an ability of steadfastness, creation and courage," said Haneya.
In Beirut, head of Lebanese militant group Hezbollah, Sayyed Hassan Nasrallah, said the "victory of Palestinians in Gaza was natural and expected", the official National News Agency reported.
"The ceasefire declaration between Israel and Gaza was an end to the Israeli aggression and a victory for the Palestinian resistance," the NNA quoted Nasrallah as saying in a televised speech.
Palestinian President Mahmoud Abbas, in a statement published by the official news agency Wafa, Abbas said he supports the agreement "to stop the bloodshed of our people and to put an end to the continuation of the Israeli aggression on Gaza".