Questions on Turning Thirty-Three by KlionskyG

Question 10

Mini-theme: II Kings

Who was King of Norway from September 1957 until his death in January 1991, a term of slightly more than 33 years? Name and regnal number required.

And note that while precisely correct spelling is not required, his regnal name does differ by just one letter from that of a different, current, world leader.

King Olav V