Profile: North Korean leader Kim Jong-un
Kim Jong-un took on the mantle of North Korea's supreme leadership with little political or military experience behind him.
Kim Jong-il, North Korea's "Dear Leader", was in the process of grooming him as his successor when he died in December 2011.
Immediately after his father's death, the younger Kim was hailed as "the great successor". He was named head of the party, state and army within a fortnight of his father's death.
Since then, he has shown he is committed to the pursuit of nuclear weapons and the advancement of North Korea's missile programme.
He has also shown himself to be ruthless with the purge of his powerful uncle and the murder, widely attributed to an order from him, of his half-brother.
'Morning Star King'
Kim Jong-un, the youngest son of Kim Jong-il and his third wife Ko Yong-hui, was born in 1983 or 1984.
He was initially not thought to be in the frame to take up his father's mantle. Analysts focused instead on his half-brother Kim Jong-nam and older full brother Kim Jong-chol.
However Kim Jong-nam's deportation from Japan in May 2001 and middle brother Kim Jong-chol's reported "unmanliness" improved his chances.
Analysts saw him as the coming man after he was awarded a series of high-profile political posts.
Swiss-educated like his brothers, Kim Jong-un avoided Western influences, returning home when not in school and dining out with the North Korean ambassador.
After his return to Pyongyang, he is known to have attended the Kim Il-sung Military University.
His mother was thought to be Kim Jong-il's favourite wife, and she clearly doted on her son, reportedly calling him the "Morning Star King".
In August 2010, when Kim Jong-il visited China, one report said Kim Jong-un had accompanied his father on the trip. By then he was widely seen as the heir-apparent and when Kim Jong-il died, this was quickly confirmed.
Mr Kim made his first public speech as North Korea marked the 100th anniversary of the birthday of founder Kim Il-sung on 15 April 2012, praising the "military first" doctrine and vowing the time his nation could be threatened was "forever over".
"Superiority in military technology is no longer monopolised by imperialists," he said, adding: "We have to make every effort to reinforce the people's armed forces."
Under him, the development of North Korea's nuclear and missile programmes has continued and appears to have made rapid strides. Three more nuclear tests have taken place, bringing the regime's total to five. Experts remain divided on how close it is to its goal of miniaturising a nuclear warhead to mount on a missile.
The reach of North Korea's missiles also appears to have increased. In July 2017 the regime test-fired two ICBMs thought to be capable of reaching western parts of the US, leading to a surge in tensions with the Donald Trump-led administration and an intensified UN sanctions regime.
In world politics, however, Kim Jong-un is still regarded as an unknown quantity. He has not travelled abroad in an official capacity since taking power, in contrast to his father who made several visits to China.
Domestically, his repeated replacement of defence ministers - there have been at least six men in the post since 2011 - is seen by some analysts as an indication of Mr Kim's lack of confidence in the loyalty of the armed forces.
And the most high-profile indication of a possible power struggle within the North Korean elite came in December 2013, when Kim Jong-un ordered the execution of his uncle Chang Song-thaek. State media said he had been plotting a coup.
Mr Kim is also widely believed to have ordered the murder of his exiled half-brother, Kim Jong-nam, in February 2017 at Kuala Lumpur International Airport.
Not much was known of Mr Kim's personal life until television footage of an unidentified woman attending events with him surfaced. In July 2012, state media announced that Mr Kim was married to "Comrade Ri Sol-ju".
Little is know of Ms Ri, but her stylish appearance led some analysts to suggest that she was from an upper-class family and that she fits Mr Kim's efforts to project a more relaxed image compared to his predecessors.
Details surrounding the marriage of Mr Kim to Ms Ri remain unclear. Most reports had suggested that Ms Ri may have been a singer who caught Mr Kim's attention during a performance.
American basketball star Dennis Rodman, who met Mr Kim in 2013 and 2014, told The Guardian newspaper that the couple had a daughter.
Mr Kim's sister, Kim Yo-jong, holds a senior post in the Workers' Party of Korea. It is not known whether his elder brother, Kim Jong-chol, holds an official role.