Saudi Arabia, which is home to Islam's holiest sites, said through its official SPA news agency on Sunday that the Supreme Court had announced "Monday, March 11, 2024, the beginning of the blessed month of Ramadan for this year."
Ramadan is one of the five pillars of Islam.
After the sighting of the crescent moon, the United Arab Emirates and Qatar also announced a Monday start for Ramadan, through their own official news outlets.
Egypt's Islamic advisory body the Dar al-Ifta also confirmed Ramadan would begin on Monday, as it will in the Palestinian Territories including Gaza.
Iran had earlier set the beginning of Ramadan for Tuesday after its "Estehlal" moon observation office said it had not been possible to observe "the crescent of Ramadan."
In Saudi Arabia, the start of the holy month had been cast into doubt after some of the kingdom's observatories reported that the moon was obscured by "cloudy weather and dust particles."
But final confirmation of the sighting came through the Al Majmaah University Astronomical Observatory in Riyadh.
As he announced Tuesday as the start of Ramadan in Jordan, the kingdom's Grand Mufti Ahmed Hasnat asked God to "relieve the anguish of our oppressed people in Gaza" and "lift affliction and aggression from them."
Oman and Libya will also mark the first day of Ramadan on Tuesday.
'Completely different'
During Ramadan, observant Muslims refrain from eating and drinking from dawn to dusk, and traditionally gather with family and friends to break their fast in the evening.
It is also a time of prayer, when the faithful converge in large numbers at mosques, especially at night.
The war between Israel and Hamas in the Gaza Strip has cast a long shadow over festivities in the region, with hopes dashed that a ceasefire agreement could be reached before Ramadan began.
At a market in Rafah, the southern Gaza city where nearly 1.5 million people have sought refuge, Palestinians on Sunday bemoaned food shortages and wartime uncertainty hanging over the holy month.
"Of course, this Ramadan is completely different from all the Ramadans that have gone before it," said Bassel Yassin, an agricultural engineer.
Hassuna Tabib Hassnan, a dentist displaced from Gaza City in the north, said he didn't know how the month will end — "in our homes, in a tent, by the sea in the north or in the south."
Hassnan added: "We had hoped that for Ramadan (we) would be in our homes, but unfortunately it is clear that we will live in displacement, pain and oppression."
The war was triggered by the October 7 attack by Hamas militants on southern Israel which resulted in about 1,160 deaths, mostly civilians, according to an AFP tally based on official Israeli figures.
Israel's retaliatory offensive in Gaza, aimed at destroying Hamas, has killed at least 31,045 Palestinians, mostly women and children, according to the health ministry in the Hamas-ruled territory.
The United Nations has warned that famine in the Palestinian territory is "almost inevitable" unless something changes in the war, with aid trickling in at levels far below the pre-war norm.
Shopping at a Riyadh mall, Saudi government employee Faisal, who preferred to give only his first name because of the sensitivity of the matter, said it was "the worst Ramadan I have ever experienced in my life."
The man, in his fifties, added: "I feel ashamed as I shop for meat and chicken for my family, while the people of Gaza are in famine."