Kim was initially considered inexperienced. However, he quickly demonstrated his determination to consolidate his power by having his uncle executed and his potential rivals purged. Many were afraid of a second Korean War after his recent string of missile and nuclear tests.
Kim changed gears once again, and held landmark nuclear disarmament summits alongside then-U.S. President Donald Trump. However, their diplomacy was ruined by disputes over U.S.-led Sanctions. With the growing pandemic and sanctions, Kim sealed off his country's borders to try and fix its failing economy.
Here's a look back at Kim's key moments as he enters his second decade of power.
Jan. 8, 1984: Kim Jong Un, the third son of Kim Jong Il, is born.
September 2010: The first public mention of Kim Jong Un's name in state media is that he has been named a four-star general by the State Media.
October 2010, Kim Jong Un makes a public appearance at a military parade. He stands next to his father, who is gaunt and stoic, on a balcony. As missiles, tanks, and soldiers move by, Kim Jong Un smiles, waves, and claps.
Dec. 17, 2011, Kim Jong Il, 69, dies. However, the news is kept secret for at least two days.
Dec. 19, 2011, 12:59 p.m. State television broadcasts Kim Jong Il's passing. State media call him "great successor", and Kim Jong Un's name is first on the National Funeral Committee's list.
Dec. 30, 2011, Kim Jong Un is proclaimed the supreme commander for the North's 1.2million-strong military. This is his first top position since the death of his father. He assumes leadership roles at other important organizations, such as the Workers' Party and National Defense Commission.
July 2012: North Korean military chief Ri Yoong Ho is fired from all high-ranking posts in what's being called Kim Jong Un’s first major purge.
December 2013, Kim's uncle Jang Song Thaek is executed on treason, corruption, and other charges. This remains the most prominent such action of Kim's rule.
May 2015: South Korea’s spy agency claims that Kim Jong Un executed Hyon Yong Chol (Armed Forces Minister) with an anti-aircraft weapon. He had complained about Hyon Yong and slept during a meeting Kim presided.
February 2017, Kim Jong Nam is the half-brother to Kim Jong Un. VX nerve agent was smeared on Kim's face. Two Asian women are taken into custody, but South Korea's spy agency accuses North Korea. The North denies any involvement.
December 2012: North Korea claims it has launched a long-range rocket to put a satellite in orbit. This launch by North Korea is considered a prohibited test of missile technology by the U.N.
February 2013, North Korea conducts its third nuclear testing, the first atomic bomb blast under Kim's leadership.
2016: North Korea conducts two more nuclear tests, and launches its second satellite successfully.
July 4, 2017, North Korea conducts the first flight test for an intercontinental ballistic weapon. Kim refers to it as "a package of gifts" that North Korea has prepared for the U.S. Independence Day. North Korea launches two more ICBMs in 2017.
August 2017, Trump warns North Korea that it could be "met with fire and fury unlike the world has ever seen." North Korea then responds by threatening to launch missiles at the U.S. territory Guam.
September 2017: North Korea conducts its sixth nuclear test, and it's the most powerful. It claims that it is a hydrogen bomb which can be used to destroy an ICBM.
April 2018, Kim Jong Un meets with South Korean President Moon Jae In at the third summit between rival countries since 1945's division. Two more summit talks are held between the two leaders.
June 2018, Singapore: Trump and Kim Jong Un meet for the first summit of leaders from the United States of America and North Korea since the Korean War of 1950-53. Kim promises to work towards complete denuclearization on the Korean Peninsula, without providing a roadmap or timetable.
February 2019, Kim Jong Un and Donald Trump meet in Hanoi, Vietnam for their second summit. Because of U.S.-led sanctions against North Korea, the meeting is canceled.
June 2019, Kim Jong Un meets Trump at the tense Korean frontier, but their third meeting impromptu does not produce any major breakthrough.
June 2020: North Korea demolishes an empty interkorean liaison office on its territory as a show of anger at a South Korean civil leafleting campaign. This is North Korea's most outrageous act since its 2018 nuclear diplomacy agreement with Washington and Seoul.
January 2021: Kim Jong Un acknowledges that his economic development plans failed at the North's first Workers Party congress in five year. He also threatened to increase his nuclear arsenal and create more advanced weapons as a protest against what he called U.S. hostility.
April 2021: Kim Jong Un declares that his country is in its "worst ever situation" due to the pandemic, persistent sanctions, and natural disasters.
October 2021: Kim Jong Un promises to build an "invincible military" during a rare weapons show that features long-range missiles capable reaching the U.S. homeland.