This year's celebration, for many, is marred by Israel's war on Gaza.
Saudi officials have spotted the crescent moon and declared it the holy fasting month of Ramadan for many of the world's 1.8 billion Muslims.
Officials sighted the moon on Sunday night, making Monday the first day of the fasting month, Saudi state television reported.
The month involves Muslims abstaining from food and drink from sunrise to sunset while reflecting more deeply on their faith and holding family gatherings. This year's celebration, for many, is marred by Israel's war on Gaza.
After officials in Sunni-majority Saudi Arabia sighted the moon, many Gulf Arab nations, as well as Iraq, Syria and Egypt, followed the announcement to confirm that they too would begin fasting on Monday.
However, some Asia-Pacific countries, including Australia, Brunei, Indonesia, Malaysia and Singapore, said they will start Ramadan on Tuesday after failing to see the crescent moon.
Oman, on the eastern tip of the Arabian Peninsula, similarly announced that Ramadan would begin on Tuesday. Jordan will also begin Ramadan on Tuesday.
Ramadan operates according to a lunar calendar. and moon sighting methodologies often vary between countries, meaning some nations declare the start of the month earlier or later.
Saudi King Salman made specific reference to the war in Gaza in comments following the Ramadan announcement.
“As it pains us that the month of Ramadan falls this year, in light of the attacks that our brothers in Palestine are suffering, we highlight the need for the international community to assume its responsibilities, put an end to these brutal crimes and provide safe humanitarian assistance . and relief corridors,” the king said.
Saudi Arabia had been urging its public to watch the skies since Sunday night in preparation for the sighting of the crescent moon.
In Iran, which is considered the world leader of Shiite Muslims, authorities typically start Ramadan a day after Sunni begins. The office of Iran's Supreme Leader Ayatollah Ali Khamenei announced that Ramadan will begin there on Tuesday, according to state news agency IRNA.
During Ramadan, those who observe eat before dawn, or “suhoor,” to sustain themselves during the daylight hours, and then break the fast with an “iftar,” often a large meal.
During the month, Muslims try to avoid conflict and focus on acts of charity. However, Israel's war in the Gaza Strip looms large for many Muslims. There were hopes that a ceasefire agreement between Israel and the Palestinian group Hamas could be reached before Ramadan began.
More than 31,000 people have been killed in the Israeli assault on Gaza, according to Palestinian health authorities in the besieged territory, and aid agencies have warned of impending famine in parts of the Gaza Strip.
Hassuna Tabib Hassnan, a dentist displaced from Gaza City in the north of the besieged Gaza Strip, told the AFP news agency: “We were hoping that by Ramadan [we] “We would be in our homes, but sadly it is clear that we will live in displacement, pain and oppression.”
Meanwhile, Israeli restrictions on Muslims praying at Jerusalem's Al-Aqsa Mosque, Islam's third-holiest site, may also further raise tensions in the region.
