Leading a country is, literally, among the toughest jobs in the world.
Usually it takes years of work, plentiful donations, hundreds of media apperances and hours upon hours of attending incredibly dull community events.
Interestingly, The Economist reported in 2011 many world leaders were getting younger - even as the populations of their countries age, reports News.com.au.
In fact, there are currently 12 world leaders under the age of 40.
Jacinda Ardern became a politician in 2008, and describes herself as a social democrat and a progressive who supports a welfare system for "those unable to support themselves".
She worked as a researcher and advisor at home, for former New Zealand Prime Minister Helen Clark, and in the United Kingdom for former British Prime Minister Tony Blair.
She grew up in the towns of Morrinsville and Murupara in the North Island and was raised Mormon, but left the church because of its stance on homosexuality and now considers herself agnostic.
Ms Ardern became leader of New Zealand's Labour Party in August, and made headlines for shutting down a radio presenter who asked about her plans to start a family just six hours after she took the job.
She loved metalwork and history in school and is a fan of whisky.
Kim Jong-un has been Chairman of the Workers' Party of Korea and supreme leader of North Korea since his father, Kim Jong-il, died of a heart attack in 2011.
It's believed he was just 27 years old at the time.
Not much is known about his early life, except that he reportedly went to an English-language boarding school in Switzerland and loves to watch basketball.
It's believed he has three children, the last one born as recently as February this year after his wife, Ri Sol-ju, disappeared from public for several months.
The dictator is believed to have ordered the executions of at least 340 people since he took power, for reasons as trivial as napping or having a bad attitude.
Mr Kim's government is currently developing a nuclear weapons arsenal, and today his government issued a letter to Australia, asking our politicians to turn against US President Donald Trump.
French President Emmanuel Macron used to be an investment banker, who founded a centrist political party called En Marche! last year.
His dad was a neurologist and his mum was a paediatrician, and he's actually the first member of his family not to have a career in medicine.
He ventured into politics in 2012, serving as cabinet minister for former president Francois Hollande, and went from being a relative political nobody to beating far right opponent Marine Le Pen in May.
He met his wife, Brigitte Trogneux, when he was just 15 years old, she was his high school French teacher, and is 24 years older than him.
Leo Varadkar was elected Ireland's Taoiseach (pronounced Tee-sha, it basically means Prime Minister) in June.
His dad is an Indian doctor and his mum is an Irish nurse, and he followed his parents' footsteps and worked as a general practitioner for a few years.
However, once he joined his local council, he skyrocketed through the political ranks.
He's been in politics for a decade, and has previously served as the country's Minister for Social Protection, Minister for Health, and Minister for Transport, Tourism and Sport.
Mr Varadkar is the first openly gay Taoiseach in history.
He first spoke publicly about it on his 36th birthday.
"It's not something that defines me. I'm not a half-Indian politician, or a doctor politician or a gay politician for that matter. It's just part of who I am, it doesn't define me, it is part of my character I suppose," he told national broadcaster RTE.
Sebastian Kurz has just become the youngest leader on the world stage.
He leads the conservative Austrian People's Party, and his campaign focused largely on closing the country's borders and vowing to cut all benefits for foreigners.
The strategy of putting "Austrians first" propelled him to near-rockstar status.
Mr Kurz is an only child, who suspended his studies at the University of Vienna - where he studied law for seven years without getting a degree - to pursue politics.
He has served as the country's Foreign Minister since he was 27.
Volodymyr Groysman was elected Prime Minister of Ukraine in April 2016.
He is a practising Jew who has two daughters and a son, and he worked for his dad's company before running for political office in 2002.
Mr Groysman's biggest challenge is overcoming his country's corruption and reform issues, and building closer ties with the European Union.
His given name name may resemble Voldemort, but it's actually pronounced more like "Vladimir".
Estonia is a tiny former Soviet country on the Baltic Sea, bordered by Russia and Latvia, and Juri Ratas is its first centrist leader in decades.
He won office after a vote of no-confidence in the country's former leader in November, after he had been in power for 17 years.
Mr Ratas is currently trying to sure-up his country's relationship with its neighbours, because he's made it quite clear he won't bow to Russia.
He's in a bit of a tricky spot, because NATO is pretty much the only thing guaranteeing his country's security from its eastern neighbour, but US President Donald Trump has made it quite clear he's not a fan.
Mr Ratas is married with three children.
Sheikh Tamim bin Hamad Al Thani is the eight Emir of Qatar, and he rose to power after his father abdicated in June 2013.
He was born in Doha, the capital, and went to high school in England before attending the Royal Military Academy Sandhurst - the institution where all British Army officers are trained.
Most Australians know Qatar as an occasional stopover on the way to Europe, but Sheikh Tamim is working hard on raising the oil-rich country's profile by hosting a wide range of international sporting events and investing in infrastructure.
He still plays competitive badminton, and has three wives and 10 children.
Saleh Ali al-Sammad is leader of Yemen's Houti movement, the rebel group that overthrew the country's government in February 2015.
At least 7600 people were killed and 42,000 injured in the coup, which also left 70 per cent of the country in need of foreign aid.
Basically, the rebels wanted to force the country's authoritarian president, Ali Abdullah Saleh, to surrender power to his deputy.
His leadership was plagued with a separist movement in the south and attacks from Al-Qaeda as well as corruption, unemployment and food insecurity.
In the end, many ordinary Yemenis supported the rebels, overthrowing the capital Sana'a and putting Saleh Al-Sammad in power.
Jigme Khesar Namgyel Wangchuck became King of Bhutan, a tiny Himalayan country between India and China, after his father abdicated in December last year.
He was educated in the United States before attending the University of Oxford in the United Kingdom, where he studied international relations.
The King has pretty big shoes to fill - his father ascended to the throne when he was just 16, and turned Bhutan into a constitutional monarchy with an emphasis on becoming the happiest country in the world.
His wedding to Jetsun Pema in 2011 was the largest media event in the country's history, and their first child was born in February last year.
San Marino is a miniscule enclave in Italy, about three hours from Florence.
It's one of the world's oldest republics, even though it's barely bigger than a city, and is known for its medieval architecture.
It has a parliamentary style of government, with 60 members elected every five years, and it headed by two captains regent, who are elected every six months and act as heads of state during that period.
Right now, those two leaders are Enrico Carattoni, a democratic socialist, and Matteo Fiorini, a liberal centrist, who were both elected in October.
