Gotabaya Rajapaksa has fled Sri Lanka ahead of his expected resignation as president
The country's air force confirmed the 73-year-old flew to the Maldives with his wife and two security officials.
They arrived in the capital, Male, at around 03:00 local time (22:00 GMT), BBC Sinhala understands.
Mr Rajapaksa's departure ends a family dynasty that has ruled Sri Lanka for decades.
He had been in hiding after crowds stormed his residence on Saturday.
The president had earlier pledged to resign on Wednesday 13 July. On Wednesday morning officials told Reuters news agency that he had yet to submit his letter of resignation to the parliamentary speaker.
His brother, former Finance Minister Basil Rajapaksa, has also left the country, sources have told the BBC. He is said to be heading to the US.
As Sri Lankans awoke to news of the president's departure, thousands of people took to the streets of the capital, Colombo. Many gathered at Galle Face Green, the city's main protest site. Some listened to fiery speeches at a makeshift stage set up for ordinary people to take the mic.
Punctuated by cries of "Victory to the struggle" in Sinhalese, the rallying cry of the protest movement, speakers railed against a government and the leaders they feel have failed them.
One of the demonstrators in Colombo delivers a speech to the crowd
Sri Lankans blame President Rajapaksa's administration for their worst economic crisis in decades.
For months they have been struggling with daily power cuts and shortages of basics like fuel, food and medicines.
The leader, who enjoys immunity from prosecution while he is president, is believed to have wanted to flee abroad before stepping down to avoid the possibility of arrest by the new administration.
The president's departure threatens a potential power vacuum in Sri Lanka, which needs a functioning government to help start digging it out of financial ruin.
Politicians from other parties have been talking about forming a new unity government but there is no sign they are near agreement yet. It's also not clear if the public would accept what they come up with.
Under the constitution, it's the prime minister, Ranil Wickremesinghe, who should act in the president's stead if the latter resigns. The prime minister is considered the president's deputy in parliament.
However, Mr Wickremesinghe is also deeply unpopular. Protesters set fire to his private residence on Saturday - he and his family were not inside - and he said he would resign to make way for a unity government, but gave no date.
That leaves the parliament's speaker as the next most likely to step in as caretaker president, constitutional experts say. But Mahinda Yapa Abeywardena is an ally of the Rajapaksas, and it is unclear whether the public would accept his authority.
Whoever does become acting president has 30 days to hold an election for a new president from among members of parliament. The winner of that vote could then see out the remainder of Mr Rajapaksa's term until late 2024.
On Monday, the main opposition leader Sajith Premadasa told the BBC he would be tilting for the presidency. But he also lacks public support and there is deep public suspicion of politicians in general.
The protest movement which has brought Sri Lanka to the brink of change also does not have an obvious contender for the country's leadership.
-- Courtesy of BBC News