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 advancement of North Korea's weapons programme, ordering four nuclear tests and several missile tests.
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 older 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".
Under him, the development of North Korea's nuclear and missile programmes has continued and appears to have made rapid strides. Four more nuclear tests have taken place, bringing the regime's total to six.
Pyongyang claims it has successfully tested a miniaturised hydrogen bomb that could be loaded on to a long-range missile, but experts remain divided on how advanced its programme is.
The reach of North Korea's missiles also appears to have increased. In 2017 the regime test-fired several missiles, and claimed it had tested intercontinental ballistic missiles that could reach the US - leading to a surge in tensions with the Donald Trump-led administration and an intensified UN sanctions regime.
As the animosity between the two sides rose, Mr Trump and Mr Kim engaged in an increasingly fiery war of words.
Mr Trump called the North Korean leader a "rocket man on a suicide mission" while Mr Kim called the US leader a "mentally deranged US dotard".
Yet, unexpectedly, Mr Kim offered an olive branch to South Korea in his new year's address, saying he was "open to dialogue" and might send a team to the February 2018 Winter Olympics in South Korea.
A flurry of diplomatic activity followed, with the two Koreas marching under one flag in the Olympic opening ceremony, and high-level meetings taking place between the two sides.
Two milestone meetings have now been planned: a summit between Mr Kim and his South Korean counterpart Moon Jae-in in late April, and a face to face meeting between Mr Kim and Mr Trump in May - the first of its kind between sitting US and North Korean leaders.
Ahead of the two summits, Mr Kim made his first known foreign trip as leader. He took a train to Beijing - North Korea's main ally and trading partner.
In April, Kim Jong-un said he had suspended all missile tests and would shut down a nuclear test site, because his country had achieved "nuclear weaponisation".
Although the halt was welcomed internationally, observers pointed out that Pyongyang had not pledged to get rid of its existing weapons, and has previously broken promises to halt nuclear development.
Meet the Kims
Domestically, Mr Kim's repeated replacement of defence ministers - there have been at least six men in the post since 2011 - has been seen by some analysts as an indication of his 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 known of Ms Ri, but her stylish appearance led some analysts to suggest that she was from an upper-class family. Reports have suggested that Ms Ri may have been a singer who caught Mr Kim's attention during a performance.
According to South Korean intelligence, the couple have three children.
Mr Kim's sister, Kim Yo-jong, holds a senior post in the Workers' Party of Korea - and stole the limelight when she represented her brother at the Winter Olympics in the South. It is not known whether his elder brother, Kim Jong-chol, holds an official role.