Couples in Denmark with their own Danish-Australian love stories are among those celebrating the royal succession in which Frederik and his Hobart-born wife Mary become King and Queen.
The modern-day fairytale - which began in a Sydney pub during the 2000 Olympics when Mary met the Danish Crown Prince - took a major twist on New Year's Eve when Queen Margrethe II announced a surprise abdication.
Among the flag-waving masses on the streets of chilly Copenhagen on Sunday were scores of expats brimming with pride.
Leon Fischer met his Danish-born wife Susan in Adelaide and their family have called Denmark home for two years.
The couple takes Australian-Danish relations so seriously that they called one of their Australian-born sons Dane.
''We met her (Mary) in November 2022,'' Mr Fischer, wrapped in the Australian flag, told AAP outside the Danish Parliament.
"I was wearing my Aussie rugby top and she came over and spoke to me and Frederik noticed and we talked rugby."
Ms Fischer noted Mary now spoke English with a Danish accent.
''Everybody loves her,'' she said.
The day is a celebration of great Danish-Australian love stories, said former Sydney-sider Drew Fremlev Fisher, 37, who moved to Denmark in 2015 where he met and married his Danish husband Kenneth.
''(Mary's) an Aussie who moved to Denmark, I'm an Aussie who moved to Denmark, she fell in love with a Dane, I fell in love with a Dane,'' Mr Fremlev Fisher told AAP, praising Mary's support for Denmark's LGBTQI community.
Brisbane biomedical science graduate Ebony Wilson, 25, and her grandmother Judy bought a last-minute plane ticket to Copenhagen on Wednesday to be part of the moment in history.
''I was thinking about it and then I thought, why not be spontaneous?'' she told AAP in Copenhagen.
"It's a once-in-a-lifetime opportunity."
Melbourne-born Stewart Mullin has lived in Denmark for 25 years after meeting his Danish wife Vibeke on a road trip to Uluru.
He first encountered the royal couple days before their 2004 wedding at an event for Australian expats.
''Even though it was the biggest day of their lives, they were just really cool and down to earth,'' he told AAP.
Since then, Mr Mullin, who works in the wind energy sector, has joined the royal couple on several Danish international trade delegations.
''Prince Frederik is such a person of the people ... he seems very Australian in his approach,'' he said.
''(Mary is) very caring and compassionate ... she'll make a lovely Queen.''
Australian lawyer Matthew Thorn, 28, who grew up in Melbourne and had a pen pal long-distance relationship with his now Danish wife Regine, said he was impressed by Mary's quick mastery of the tricky-to-pronounce Danish language.
''She makes Australians proud,'' he told AAP.
