Prince Harald was born at the Skaugum estate in 21 February 1937.

He was baptized in the Royal Chapel of the Royal Palace in Oslo on 31 March 1937 by Bishop Johan Lunde.

In 1940 the entire royal family had to flee Oslo because of the German invasion. It was deemed safer for the family to split up. The King and Crown Prince Olav would remain in Norway and the Crown Princess was to make her way to Sweden with the three children. The latter party reached Sweden on the night of 10 April. but although Crown Princess Märtha was Swedish-born, they encountered problems at the border station.

Harald spent the following days in Sälen before moving to Prince Carl Bernadotte's home in Frötuna on 16 April.

On 26 April the group moved to Drottningholm in Stockholm.

On 17 August the Crown Princess and her children left for the United States from Petsamo, Finland, aboard the United States Army transport ship American Legion.

In the autumn of 1945, he was enrolled in third grade of Smestad skole as the first member of the royal family to attend public school.

Prince Harald returned to Norway with his family at the war's end in 1945.

In 1954 tragedy struck as he lost his mother to cancer. The Crown Princess's death was a tremendous loss for him and his family as well as for Norway.

Harald attended the Council of State for the first time on 27 September 1957 .

He took the oath to the Constitution of Norway on 21 February 1958. In the same year, he also served as regent in the King's absence for the first time.

He graduated from Oslo katedral skole and in the autumn of that year, Harald began studies at the University of Oslo. He later attended the Cavalry Officers' Candidate School at Trandum, followed by enrollment at the Norwegian Military Academy, from which he graduated in 1959.

In 1960, Harald entered Balliol College, Oxford where he studied history, economics and politics. He was a keen rower during his student days at Oxford and was taught to row by fellow student and friend Nick Bevan, later a leading British school rowing coach.

In 1960, he also made his first official journey abroad, visiting the United States in connection with the fiftieth anniversary of the American Scandinavian Foundation.

The Crown Prince carried the Norwegian flag at the opening parade of the 1964 Summer Olympics. He represented Norway in the yachting events of the Summer Olympics in Tokyo in 1964, Mexico City in 1968, and Munich in 1972.

Harald married a commoner, Sonja Haraldsen, at Oslo Domkirke in Oslo on 29 August 1968. The pair had dated for nine years and were only allowed to marry when Harald gave his father the ultimatum that if he was not allowed to marry Sonja he would not marry at all, which would have ended the reign of his family and the Norwegian monarchy, as Harald was the sole heir to the throne.

On the death of his father on 17 January 1991, Harald succeeded automatically to the Norwegian throne. He became the first Norwegian-born monarch since Magnus VII abdicated in 1343, a gap of 648 years.

The King chose to continue the tradition of royal benediction, a tradition that had been introduced with his father, and was consecrated together with Queen Sonja in the Nidaros Cathedral on 23 June 1991.

Until 2012, the King of Norway was, according to the constitution, the formal head of the Church of Norway. The constitutional amendment of 21 May 2012 made the King no longer the formal head, but he is still required to be of the Evangelical Lutheran religion.

In 2015, he became the world's first reigning monarch to visit Antarctica, specifically the Norwegian dependency Queen Maud Land.

When the King and Queen turned 80 years in 2017, the King decided to open the former royal stables to the public as a gift to his wife, the Queen. The new venue was named The Queen Sonja Art Stable and is the first institution owned by the royal family which is permanently open to the public.

On 8 May 2018, the King's constitutional status as holy was dissolved, while leaving his sovereign immunity intact.