Jammeh was defeated in December's election by Adama Barrow but he went on to challenge the results.
But two days after Mr Barrow was sworn in, Jammeh left on a plane reportedly bound for Guinea.
Barrow has been in neighboring Senegal for days and was inaugurated as president in the Gambian embassy there on Thursday.
Troops from several West African nations, including neighboring Senegal, had been deployed in The Gambia, threatening to drive Jammeh out of office if he did not agree to go.
Jammeh's decision to quit came after talks with the presidents of Guinea and Mauritania.
Guinea's President Alpha Conde is with Jammeh and his wife on the plane that left Banjul late on Saturday.
In an address on state television, Jammeh said he would stand down and that it was "not necessary that a single drop of blood be shed".
Jammeh arrived at Banjul Airport amid a large convoy of vehicles and throngs of cheering supporters.
He stood on a small platform to hear ceremonial music performed by a military band and then walked down a long red carpet surrounded by dignitaries.
He climbed the steps to the plane, turned and kissed and waved a Koran at those assembled.
After 22 years in power, he left bound for Guinea where it's believed he will stay before going on to another country.
Soldiers and other dignitaries were emotional as he left - many of them crying.
The details of the arrangements made - or promises offered to persuade him to give up power peacefully are not yet known, but there was the real threat of military action from regional states.
He's the first president to peacefully hand over power in The Gambia since independence from Britain in 1965.
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All rights reserved to Arab Today Media Group 2021 ©
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