Police in the capital confirmed the arrest, with the charge relating to "sexual intercourse with someone who is unconscious or for other reasons is unable to resist the act."
Marius Borg Hoiby, the 27-year-old son of Norway’s Crown Princess Mette-Marit, was arrested on Monday in Oslo.
He is facing serious charges, including one of rape.
Police in the capital confirmed the arrest, with the charge relating to "sexual intercourse with someone who is unconscious or for other reasons is unable to resist the act."
Alongside this charge, Hoiby faces additional accusations of "abuse in close relationships," breaching a restraining order, and driving without a valid driver’s licence, NBC News reports.
A preliminary charge allows police to detain suspects for further investigation. He is currently being held by authorities in Oslo.
Hoiby’s defence attorney, Oyvind Bratlien, confirmed to Norwegian state broadcaster NRK that his client denies the charge of rape, stating that Hoiby is cooperating with the police and wishes to explain his side.
The Royal Palace, through Communications Advisor Simen Sund, declined to comment, directing all questions to police and Hoiby’s legal representatives.
It was the police who initiated the provisional rape charge, rather than the alleged victim, with her lawyer, Hege Salomon, confirming the woman was not connected to the other alleged victims in the case.
She has, however, been “having a hard time,” Salomon told Aftenposten.
Hoiby is under investigation in relation to allegations of abuse involving four women. His arrest follows a violent incident in August at an apartment in Oslo's Frogner district, where he pleaded guilty to bodily harm and property damage, with police suspecting domestic abuse.
He has also pleaded guilty to making a death threat in a separate incident, but has denied other allegations tied to two past relationships.
On Monday, police reported that Hoiby was arrested in a car with the woman from the August incident.
At the time of his earlier arrest, he had apologised for his actions, attributing them to being intoxicated with alcohol and cocaine after an argument, alongside mental health struggles, which he promised to address through treatment.
Though not an official member of the royal family, Hoiby has long been part of the public royal circle. Born in 1997, he was just four years old when his mother married Prince Haakon in 2001.
He has attended royal events and lived with his mother, stepfather, and half-siblings, Princess Ingrid Alexandra and Prince Sverre Magnus, on royal property.
Hoiby’s personal life has attracted media attention before. He previously sold designer items on a Norwegian resale app, listing the royal palace as his address, and made a brief appearance in a popular Norwegian teen TV show.
In 2018, he featured in American Vogue, offering fashion advice on stylish Oslo locations.
His stepfather’s sister, Princess Martha Louise, who married an American self-proclaimed "shaman" in August, is also frequently in the tabloids, with her claims of communicating with angels.