Denmark's popular Australian-born Crown Princess Mary will become queen on 14 January when her husband Crown Prince Frederik accedes to the throne after his mother's abdication, capping her real-life fairytale.

Born in Hobart, Australia, on February 5, 1972, Mary Donaldson was working as an advertising executive in Australia when she met the future king while out with friends at Sydney's Slip Inn bar, during the Summer Olympics in 2000.

She only discovered later that he was the crown prince of Denmark and his group of friends was made up of other European royals– including his younger brother Prince Joachim and cousin Prince Nikolaos of Greece and Denmark.

"The first time we met, we shook hands," she said in an interview several years ago.

"I didn't know he was the prince of Denmark. Half an hour later, someone came up to me and said, 'Do you know who these people are?'"

After a discreet long-distance relationship and numerous under-the-radar visits, the couple became officially engaged in October 2003 and married on 14 May 2004 in Copenhagen Cathedral. 

They are now parents to four children: Prince Christian, 18, who will one day become king after his father, Princess Isabella, 16, and twins Prince Vincent and Princess Josephine, who turn 13 next week. 

Mary will become queen on 14 January, after Margrethe II announced in her annual New Year's Eve speech on Sunday that she would abdicate in favor of her son, citing age and health issues.

Modern and trendsetter

The abdication announcement came as a surprise, as Margrethe had repeatedly insisted over the years that she would never abdicate.

She is currently Europe's longest-reigning monarch and will have served for 52 years to the day when she steps down.

Mary made a splash in Denmark from the start, impressing Danes with her ability to learn the Danish language quickly.

A poll published by Danish television TV2 in December declared her Denmark's third-most popular royal, behind the immensely popular queen and Mary's husband Frederik.

She is often compared to Britain's Crown Princess Kate for her sense of fashion style and long dark locks, regularly making the best-dressed pages of Danish and international magazines.

She is also known for her work in fighting bullying, domestic violence, and social isolation, as well as promoting mental health and women's rights.

Mary and Frederik are considered a modern couple, who love pop music, modern art, and sports, according to historian Sebastian Olden-Jorgensen.

They have tried to give their four children as normal an upbringing as possible, sending them mainly to state schools.

Their first-born, 18-year-old Prince Christian, was the first Danish royal to attend daycare.

They "do not represent a potential revolution compared to the queen", but a careful transition adapting to the times, Olden-Jorgensen said.

Mary has made regular visits back to Australia with her husband and children over the years, where she is keenly followed by the media.