The former monarch was the nephew of the late Prince Philip, a friend of King Charles, and spent the majority of his years in exile in London before returning to his country.
Constantine, the former and final monarch of Greece, died at the age of 82 in an Athens hospital, his doctors reported.
The nephew of the late Duke of Edinburgh and godfather to Prince William, Constantine, was treated in the intensive care section of the private Hygeia Hospital in the Greek capital.
The hospital staff had no additional information pending an official announcement.
The former monarch ascended the throne as Constantine II at the age of 23 in 1964. After winning an Olympic gold medal in sailing with two other Greek sailors at the age of 20 in Rome.
He began his reign as a wildly popular king but lost most of that support the following year. As a result of his role in the plots that brought down the popularly elected Center Union government of George Papandreou.
Prince William’s godfather Constantine, 82, dies.
After Constantine clashed with military leaders, he was eventually pushed into exile, and in 1973, the dictatorship abolished the monarchy.
When democracy was reinstated in 1974, a vote destroyed Constantine’s dreams of regaining the throne.
He was able to spend his final years in his native land and became a rather uncontroversial historical figure.
Constantine was the nephew of Greek-born Prince Philip, the late Duke of Edinburgh. Who was born on June 2, 1940, in Athens.
While admitting that Greece was now a republic, Constantine continued to style himself as king of Greece and to refer to his children as princes and princesses, even though Greece no longer recognized such titles.
The majority of his years in exile were spent in London’s Hampstead Garden Suburb. Where he was reported to have been especially close to his second cousin, now King Charles.
Constantine is survived by his wife, the former Princess Anne-Marie of Denmark, the youngest sister of Queen Margrethe II. Also his five children, Alexia, Pavlos, Nikolaos, Theodora, and Philippos, and nine grandchildren.
