The youngest child of King Carl XVI Gustaf, the Duchess of Hälsingland and Gästrikland, is unlikely to ever become the nation’s head of state, being fourth in the line of succession behind her sister Victoria, her niece Estelle and her brother Carl Philip.
Her distance to the royal castle widened in 2010, when she moved to New York to nurse a broken heart after breaking off her engagement to lawyer Jonas Bergström.
That’s where she met O’Neill, a businessman eight years her senior working for hedge fund Noster Capital.
At university, Madeleine took courses in art history, ethnology, history and law. Since her first work placement with UNICEF in 2006, her work has focused on children’s rights and well-being.
IN PICTURES: Princess Madeleine through the years
In New York, she has a full-time, unpaid position with the World Childhood Foundation, a charity for marginalised children set up by her mother in 1999.
A modern, unpretentious style has helped the Swedish monarchy stay popular but Madeleine’s penchant for glamorous fashion and a reputation for partying has tarnished her image in the egalitarian Nordic country.
Her hobbies reflect an upper class background: horse riding, art, theatre and skiing.
The soon to be 31-year-old was the least liked member in a survey carried out by TNS-Sifo in December last year. On a scale of one to five, she scored just 2.8, compared with 3.0 for her brother, 3.3 for her father and lagging her sister’s 4.2 points.
Pollster Jon Andersson attributed the result to “the fact that the princess has not had an especially strong presence in Sweden and didn’t appear in the media”, unlike Victoria, whose every move in Stockholm is closely followed by journalists.
The announcement of the engagement in October revived some of the media’s interest in her, especially since little was known about O’Neill.
Elisabeth Tarras-Wahlberg, a former director of the royal court’s press department, told daily Svenska Dagbladet the New York financier was “a stable person, mature”.
But O’Neill sparked controversy in November last year when he made an obscene gesture at a paparazzi photographer.
“Chris does not seem to understand his role,” historian and family friend Herman Lindqvist told tabloid Aftonbladet.
Since then, many Swedes view the London- and Switzerland-raised securities analyst with suspicion.
He has declined taking a royal title, which would require him to become Swedish and give up his job, and the couple are expected to return to New York after their honeymoon.