"His Majesty the King is in fine form and left Oslo University Hospital this morning," the palace said in a briefly-worded statement.
The monarch was hospitalised on Friday for an infection but no other details were disclosed.
King Harald V is the grandson of Haakon VII, the first king of Norway after the 1905 dissolution of a union with Sweden. He became king in 1991 on the death of his father.
In 2003, he underwent surgery for bladder cancer, and had another operation in 2005 on a cardiac valve.