Sweden's King Carl XVI Gustaf and Queen Silvia have tested positive for Covid-19, the palace said on Tuesday.
Both are in their 70s and therefore in a high-risk category.
"The king and queen, who are fully vaccinated with three injections, have mild symptoms and are feeling well, given the circumstances," the palace said.
“The royal couple have isolated themselves at home in accordance with the rules, and contact tracing is ongoing."
The 75-year-old king and his 78-year-old wife are the latest members of Sweden’s royal family to contract the virus.
Last March, the couple’s eldest daughter, Crown Princess Victoria, and her husband Prince Daniel tested positive.
In November 2020, the king and queen’s son Prince Carl Philip and his wife Princess Sofia were infected with the coronavirus.
Sweden, like many other European nations, has been hit by a new wave of Covid-19 infections in recent weeks, spurred on by the Omicron variant.
Omicron is more transmissible than the Delta variant but causes less severe symptoms.
The country registered 11,507 cases on December 30, health agency data showed on Tuesday, as a fourth wave of the virus puts health care under renewed pressure.