Sheikh Hamad bin Khalifa Al Thani ruled since overthrowing his father in 1995 and played key role in arming Syrian rebels
The emir of Qatar, the world's richest country per capita, has handed over power to his Harrow-educated son in a rare peaceful transition for the tiny but globally influential Gulf state.
In a short speech on state television, Sheikh Hamad bin Khalifa Al Thani, who has ruled since overthrowing his father in 1995, said the moment had come for a new generation to take over
"The time has come to open a new page in the journey of our nation that would have a new generation carry the responsibilities ... with their innovative ideas," said the 61-year- old sheikh.
"I address you today to inform you that I will transfer power to Sheikh Tamim bin Hamad Al Thani. I am fully confident that he is qualified for the responsibility and is trustworthy."
State television later showed streams of wellwishers greeting the outgoing emir and Sheikh Tamim at the royal court.
The emir did not specify when the change would take effect but a Qatari official had said the move would take immediate effect.
Sheikh Hamad, who has ruled since overthrowing his father in 1995, convened relatives and advisers in the Qatari capital, Doha, on Monday to reveal plans for his departure.
Unusually, news of the conclave was reported by al-Jazeera TV, which is owned by the government and usually avoids Qatari affairs.
Qatar has played a major role arming the rebels seeking to overthrow Syria's Bashar al-Assad, so the transition will be closely watched for signs of any policy shifts.
But Sheikh Hamad made no mention of the public face of Qatar's assertive foreign policy, prime minister and foreign minister Sheikh Hamad bin Jassim, a veteran politician who had been expected also to step down.
The new emir, Sheikh Tamim, 33, was educated at the English public schools Harrow and Sherborne before graduating from the Sandhurst military academy.
The move is a rare example of a Gulf leader who has stood aside of his own free will. But it does not appear to herald an outbreak of democracy in an area dominated by absolute monarchies that have been shaken by the Arab spring while resisting reform at home.
"This contributes another page to the chapter of the Arab spring, but it is not necessarily people power that has brought it about," said Salman Shaikh, of the Brookings Centre in Doha. "This is family transition based on traditional values, rather than a strictly democratic one."
Under the emir's rule, Qatar was transformed from a sleepy and underdeveloped backwater in the shadow of neighbouring Saudi Arabia to become a global political and financial power – with a native population of just 300,000, who enjoy the highest per capita income in the world.
Today it is the world's largest exporter of liquefied natural gas and has a sovereign wealth fund estimated to be worth $200bn (£130bn). It is also hosting the 2022 World Cup.
Diplomats and friends of the emir say he has been speaking privately about his plans for more than a year, including during a visit to Washington in April.
Qatar has played a central role in supporting the Arab uprisings of the past two years, extending armed support to the Libyan rebels fighting to overthrow Muammar Gaddafi and doing the same with the opposition to Assad.
But it has also been heavily criticised for its support for the Muslim Brotherhood, which is now in power in Egypt and Tunisia. In Damascus the emir is a hate figure, and stands accused of backing extreme Islamist rebel groups and of conspiring along with the US and Israel.
Even before the uprisings, Qatar was famous for its dextrous diplomacy and readiness to mediate in regional conflicts. It hosts a huge US airbase while also maintaining cordial relations with Iran.
Gulf sources say Sheikh Tamim is less keen than his father on the Brotherhood, but most observers predict continuity on key policies. "Tamim has matured a lot," said a family friend. "He will continue what his father started. He is a military man, and he is disciplined."
The emir's plans to step down were delayed by health problems – he is thought to have undergone a kidney transplant – and by the escalating crisis in Syria.
Even before confirmation that he was stepping down, social media users posted messages praising him.
"He's saying: 'Arab spring or no Arab spring – I am handing over to my son,'" said Saad Djebbar, a London-based lawyer who knows Qatar well. "But the emir put Qatar on the map, in colour. He has left the country with the highest per capita income in the world. Who had even heard of it before he was in charge? He had a vision, unlike his own father.
"This will change the traditional mindset in the region, where rulers stay until they die. Look at Saudi Arabia. The king is 90 and there is still resistance to change from one generation to another.
"With al-Jazeera he [the emir] ended the era of stagnant, one-sided Arab media. Now he is telling the others: 'Give youth a chance' – even though power stays in the family. It will lead to other changes."
Rumours were circulating of other surprise announcements, leading to speculation that Tamim might introduce constitutional changes after elections to an advisory council next year.
But on the eve of the power transfer, Sheikh Hamad issued a decree extending the term of the advisory Shura council, in effect indefinitely postponing elections that had been tentatively scheduled for the second half of the year.
The election would have been the first to the Shura council, 30 of whose 45 members are meant to be elected, with the others appointed by the emir, under a constitution approved in 2003. All the body's current members are appointed.
Qatar's internal affairs attract little outside attention, though human rights watchdogs have criticised the conviction of a poet accused of insulting the emir. There have also been calls for better conditions for foreign workers.
"Change at the top in Qatar will create unease in a region that is not used to the orderly abdication of rulers and key figures," said Chris Doyle of the Council for Arab-British Understanding in London.
"Other states may or may not like the precedent. The unease will be amplified by the major role Qatar has played in regional crises. Will the same policy towards Syria continue for example? Will a new generation push through the promised elections and democratic changes?"