His doctors announced that Constantine, the former and last king in Greece, died at the age of 82 in Athens.
Constantine, the nephew of the late Duke Of Edinburgh, and godfather of Prince William had been admitted to the Hygeia Hospital in Athens.
The hospital staff did not have any further information in the meantime.
After achieving an Olympic sailing gold medal at 20 years old, the former monarch was elevated to the throne of Constantine II in 1964 at the young age of 23.
Although he began his reign as a popular monarch, he lost much of his support the year after he was active in the machinations that brought down George Papandreou’s popularly elected Centre Union government.
Constantine was forced to flee after clashing against military rulers. The dictatorship ended the monarchy in 1973.
A referendum ended any hope Constantine had of reigning over again after democracy was restored to power in 1974.
For his final years, he was able to go back to his country and became an uncontroversial figure.
Constantine was born in Athens on the 2nd of June 1940. He was the nephew and Greek-born Prince Philip.
Constantine accepted that Greece was now a republic but continued to call himself the king and queen of Greece until the end. He also called his children princes or princesses despite the fact that no titles of nobility were recognized in Greece.
He spent most of his time in exile in London’s Hampstead Garden Suburb. It was where he was most closely related to his second cousin, King Charles.
Constantine is survived his wife, Princess Anne-Marie of Denmark, who was the youngest sister to Queen Margrethe II. He has five children, Alexia Pavlos, Nikolaos and Theodora; and nine grandchildren.