King Harald V is in a stable condition in hospital after developing a fever.
In a brief statement, the Royal Court said: ”His Majesty the King was today admitted to Oslo University Hospital for the investigation of fever. His condition is stable.”
No further details were given.
The King of Norway was last seen in public at a sailing competition last week. Along with the rest of his family, he has had a low public profile in recent weeks as the summer holidays continue.
Harald V, who turned 85 earlier this year, has ruled Norway since 1991.