The path to her succession to the throne on Sunday alongside husband Crown Prince Frederik can be traced to the couple's introduction at a Sydney pub during the 2000 Olympics.
He will become King Frederik X of Denmark, two weeks after his mother - 83-year-old Queen Margrethe - announced she would be the first Danish royal to abdicate in some 900 years.
Tens of thousands of people are expected to brave Copenhagen's 3C forecast temperature to catch a glimpse of the new monarchs.
Frederik and Mary met in Sydney during the 2000 Olympics. (AP PHOTO)
In Australia, there are events planned at Sydney's Slip Inn where the two first met, and in Mary's home state of Tasmania, where landmarks will be lit in recognition of the popular royal.
The Danish royal succession is set to be a low-key affair, with the main event occurring about 1am (AEDT) when most Australians will be sleeping.
Frederik becomes Denmark's head of state, Mary will be Queen and their eldest son 18-year-old Christian the Crown Prince, the moment Margrethe signs abdication papers at a state council meeting inside Christiansborg Palace, home to the Danish parliament.
King Frederik, 55, is scheduled to make his first public appearance on a balcony alongside the Danish prime minister who will formally proclaim him as the country's new regent. The public hope to also see Mary appear on the balcony.
Frederik becomes head of state, Mary queen and their eldest son 18-year-old Christian crown prince. (AP PHOTO)
Mary's Hobart-based sister, Jane Stephens, has travelled to Copenhagen.
The royal couple will ride home to their residence at Amalienborg Palace in an 1891 black-lacquered mahogany horse-drawn coach, while across the harbour military personnel will fire cannons in a three-by-27-shot honorary salute.
There will be more celebratory explosions later as Copenhagen's famed Tivoli Gardens amusement park hosts a fireworks extravaganza – the biggest in its 180-year history.
Across town, Aussie expats on the Australian Embassy's email database known affectionately as the ''Vegemite List'' will be joining Ambassador Kerin Ayyalaraju for a soiree to toast Mary's promotion.
The royal couple married in May 2004 and have four children.
22°C