ATHENS — Constantine II, the last king of Greece, who ruled for just three years during a turbulent period in the country’s modern history that culminated in the abolition of the monarchy, died on Tuesday in a hospital here. He was 82.
He had been in intensive care for several days after a respiratory infection, a family spokeswoman said.
Constantine was a popular figure when, at 23, he ascended the throne after the death of his father, King Paul, in 1964. Just years earlier he won Greece’s first Olympic gold medal in sailing in decades, at the 1960 Games in Rome.
But public support faded after he tried to influence Greek politics, machinations that led to the collapse of the newly elected centrist government of Prime Minister Georgios Papandreou.
Constantine appointed a series of defectors from Mr. Papandreou’s party as prime minister without holding elections, a widely unpopular chain of events that became known as “the Apostasy.”
The increasing instability culminated in a coup led by a group of army colonels in 1967, considered one of the darkest moments in Greece’s modern history. It set off seven years of a brutal dictatorship for which many Greeks still blame the former king.
Constantine initially accepted the junta before attempting a counter-coup in December of the same year. When it failed, he was forced to flee to Rome, where he spent the first years of his exile.
After the dictatorship ended in 1974, Greece’s new government called a referendum on the monarchy, and 69 percent of Greeks voted to abolish it. The vote effectively deposed Constantine and ended a monarchy that had ruled Greece since 1863, except for the period from 1924 to 1935, when it was first abolished and then restored.
Although Constantine professed to accept the results of the referendum as an expression of the will of the people, he continued to refer to himself as king and reportedly insisted on being addressed as “your majesty” by visitors during his exile.
A descendant of the Danish Glücksburg monarchy, Constantine was born in Athens on June 2, 1940, the only son of Crown Prince Paul of Greece and his German-born wife, Princess Frederica.
He spent his early years in exile as well, first in Egypt and then in South Africa, after the Italian invasion and Nazi occupation of Greece in World War II. His family returned to Greece after the war, in 1946.
An able sportsman during his school years, Constantine excelled in swimming, karate and riding, though it was for his sailing skills that he won international recognition.
He served in all three branches of the armed forces and studied law at Athens University.
In 1964, he married Princess Anne-Marie of Denmark, who became queen.
She survives him, as do their five children: Alexia, Pavlos, Nikolaos, Theodora and Philippos; nine grandchildren; and two sisters, Sofia, the former queen of Spain, and former Princess Irene.
In exile he lived mostly in London, where he is said to have developed a close relationship with his second cousin, Charles, now King Charles III. He was chosen to be one of the godfathers to Prince William, heir to the British throne.
Constantine did not return to Greece until 1981 — to bury his mother, Queen Frederica — but afterward he made increasingly frequent visits until relocating there permanently in 2013, first to Porto Heli, on the Peloponnese peninsula, and then to Athens. His public appearances were rare.
His relationship with the Greek authorities after his dethroning remained prickly. In 1994, the Socialist government passed a law stripping him of his nationality and expropriating the former royal family’s property. Constantine took the case to the European Court of Human Rights, which in 2002 ordered Greece to pay him and his family nearly $15 million in compensation, a fraction of what he had sought. He accused the government of acting “unjustly and vindictively.”
“They treat me sometimes as if I’m their enemy,” he said in 2002. “I am not the enemy. I consider it the greatest insult in the world for a Greek to be told that he is not a Greek.”
The former king could have regained a Greek passport by adopting a surname, which the government demanded that he do to acknowledge that he was no longer king. But he insisted on being called only Constantine, and continued to cast himself as king and his children as princes and princesses.
After his death, Greek television channels played montages of key moments of his life, from his enthronement to his swearing in of the colonels who had led the 1967 coup. But news of his death also stoked a vehement debate on social media about whether there should be a state funeral.
The government said Constantine would be buried on Monday as a private citizen on the grounds of the former royal family’s summer palace at Tatoi, north of Athens. The family spokeswoman said the burial would follow a service conducted by Archbishop Ieronymos II at the Athens Cathedral. Visiting dignitaries would include the Spanish royal family, she said.
With little nostalgia for the monarchy in Greece — a 2007 poll showed that fewer than 12 percent of its people would welcome its return — official reactions to the death were restrained.
President Katerina N. Sakellaropoulou, the country’s head of state, a largely ceremonial role, made no public statement.
The government is to be represented at the funeral by Deputy Prime Minister Panagiotis Pikrammenos and the culture minister, Lina Mendoni.
Greece’s conservative prime minister, Kyriakos Mitsotakis, said on Wednesday that Constantine’s death marked “the formal epilogue of a chapter that definitively closed with the 1974 referendum.”
He added, “It is now up to history to judge the public figure Constantine fairly and strictly.”