He's been known as the Crown Prince of Denmark since the age of three, but today he will leave Copenhagen's Christiansborg Palace as King Frederik X, sovereign of Europe's oldest monarchy, with his Australian wife Mary to become Queen.
Denmark's royal transition was sparked just weeks ago by the bombshell announcement from Queen Margrethe II on New Year's Eve, when she revealed her intention to abdicate in early 2024. The news that Frederik's hugely popular mother, the world's only reigning queen, would relinquish the throne shocked Danes across the country.
Margrethe had become Europe's longest-serving monarch on the death of Britain's Queen Elizabeth II in 2022. The pair were known to be close, and it was widely assumed that the Danish head of state, like her distant cousin, viewed her role as a job for life.
However, it seems the 83-year-old has had a change of heart and will step aside exactly 52 years to the day after she ascended the throne. So, who is Denmark's soon-to-be king and what kind of monarch will he be?
A rebellious teen
While the Danish monarchy stretches back more than 1000 years, today its royals have a limited role under the country's constitution. Danes are immensely proud of their royal family and monarchs play an important ambassadorial role.
"He's extremely popular. The polls show a very convincing support from the Danish people," Birgitte Borup, culture editor at Danish newspaper Berlingske, told CNN. "Queen Margrethe is serving him the monarchy on a silver platter."
Borup said Frederik will be "a different kind of king", explaining that he is "very down to Earth and interested in sports whereas his mother is more culturally distinguished". She added that "his main challenge might be his way with words", as he is "not known to be great at freestyling in front of a crowd".
Born in 1968, Frederik André Henrik Christian is the first child of Margrethe and her late husband, Prince Henrik, who died in 2018. His forename was chosen in line with the Danish royal custom of the heir apparent being named either Frederik or Christian. His only sibling, Prince Joachim, was born in 1969.
Growing up in the public eye was not easy for the shy young royal. He received his primary education at Krebs' Skole, an elite private school in Copenhagen, before going to boarding school in Normandy, France. Frederik was uncomfortable with the media attention and anxious about his destiny. By the early 1990s, many saw him as a "party prince" with a penchant for fast cars.
His time at Aarhus University helped rehabilitate his reputation and in 1995 he became the first Danish royal to gain a master's degree. His political science studies included a year abroad, at Harvard, where he was enrolled under the pseudonym of Frederik Henriksen – a nod to his father.
While in the US, Frederik – who is also fluent in French, English and German – earned his diplomatic stripes serving at Denmark's UN mission for several months in 1994. He was later posted to Paris for a year, as first secretary of the Danish embassy in 1998.
Accomplished athlete
Frederik has also undergone extensive military training in all three branches of the Danish military, most notably completing training in the navy's elite Frogman Corps, where he was nicknamed "Pingo" ("Penguin").
In addition to being a decorated military officer, he has shown himself to be an eager and extremely capable sportsman. Over the years, he has run multiple marathons – in Copenhagen, Paris and New York – and in 2013 he became the first royal to compete in an Ironman, finishing with a time of 10:45:32.
He was also a member of the International Olympic Committee between 2009 through 2021 and, in 2000, he took part in a four-month, 2795-kilometre dog-sled expedition across northern Greenland, an autonomous territory of Denmark.
Princess Mary's path from Tassie girl to Queen of Denmark
Frederik also gained popularity at home through his Royal Run initiative. Launched in 2018 to mark his 50th birthday, the sporting challenge has since become one of the largest running events in the nation, with more than 80,000 participants every year.
Meanwhile, much like his British counterpart, King Charles III, the 55-year-old has also become a keen environmentalist. Since Copenhagen hosted the COP15 climate talks in 2009, he has been firmly engaged in highlighting the perils of climate change and promoting Denmark's role in a greener future.
Danish royal experts say that while Frederik is popular with the public, he will face challenges upon his accession - which will see him become king and head of state of Denmark, Greenland and the Faroe Islands.
"Crown Prince Frederik is a much more informal person than his mother," said historian Lars Hovbakke Sørensen. "He needs in the future to appeal more also to Danes who are not interested in sport, by showing an interest for other issues, if he would like to keep the broad support for the monarchy."
Likewise, Danish royal author Trine Villemann told CNN that "first and foremost Frederik will have to prove that he can do more than sports".
The former royal correspondent and author of 1015 Copenhagen K, an unauthorised biography of the family, explained that "although he has said publicly for some years that he is now comfortable with his future role, deep down there is amongst many Danes still a lingering doubt and he needs to overcome that – no matter how popular he is".
Chance encounter
Frederik put his bachelor days behind him when he met Australian sales executive Mary Elizabeth Donaldson. The pair met at a rowdy Sydney pub in 2000, while the crown prince was in Australia for the Olympics. As the story goes, Mary didn't realise she was being charmed that night by real-life royalty.
Four years later, the pair wed in a lavish ceremony at Copenhagen Cathedral before a congregation of kings, queens and honoured guests and watched by millions around the world.
They now have four children: Christian, 18, who becomes Denmark's new crown prince on his father's accession, 16-year-old Isabella and 13-year-old twins, Vincent and Josephine. The couple have tried to give their children a more informal upbringing than Frederik had by sending them to regular state schools.
Speaking to CNN ahead of her 2012 Ruby Jubilee marking 40 years on the Danish throne, Queen Margrethe expressed her admiration for her daughter-in-law, saying, "I feel very confident in her. We have a very good relationship indeed, a warm relationship."
And ordinary Danes have also embraced Mary, who has been praised for her poise and commitment to social causes.
Villemann describes Mary as "the power behind Frederik" and describes her transition from commoner to beloved royal as "remarkable and impressive".
The royal expert points to several of the future queen's priorities over the years such as her work in mental health and tackling bullying and loneliness through her foundation. She explained: "I dare say that Mary has led the way for the likes of the Princess of Wales in choosing causes and spreading awareness in the way she has used her royal platform."
According to Borup, Mary will be the "greatest asset for the monarchy" in the years ahead.
"She wasn't born royal but you'd think she was. She carries herself with such grace and is an amazing representative for the nation of Denmark," she said. "She's known to always be well prepared, and she's taken on some pretty substantial tasks, such as shining a light on domestic violence.
"When Mary and Frederik met in Australia, the story used to be that she was lucky to run into a fairytale prince. I think time has shown he was even luckier."
