Juan Carlos I led Spain to democracy and foiled a military coup, but he heads into exile under a cloud of royal corruption that has ruined his legacy.
He abdicated in 2014 after playing a determining role in Spain's modern history, stepping up as the first crowned head of state in 44 years after the death of General Francisco Franco.
He took the throne within days of Franco's death in November 1975, having been named successor by the dictator himself, who passed over Juan Carlos's father, Juan de Borbon.
"Faithful to the political desire of my father... I wanted to be king for all Spaniards," Juan Carlos said in his abdication address, recalling the day of his proclamation.
He was popular for decades, however, on Monday the former head state admitted to his son King Felipe VI it was better he left the country.
"Guided by the conviction to best serve the people of Spain, its institutions, and you as king, I inform you of my decision at this time to go into exile outside Spain," Juan Carlos wrote.
Facing investigation at home and abroad for corruption, he had become an embarrassment to the throne and the government.
Felipe had accepted the decision, the royal palace said, following a Supreme Court decision in June to open an investigation.
Suspicion focuses on $100 million (85 million euros) alleged to have been paid secretly into a Swiss bank account in 2008 by Saudi Arabia.
Felipe has tried to distance himself from the allegations of a huge hidden fortune, withdrawing his father's annual royal allowance and renouncing his inheritance.
- Coup-stopper -
Yet it was Juan Carlos who had defied the Francoists by ushering in a new system of parliamentary monarchy. A new constitution was passed by referendum in 1978.
He was credited with helping to defuse an attempted coup in February 1981 by soldiers who stormed into parliament shooting and who held lawmakers hostage for several hours.
The king's appearance on television urging support for the democratic government was instrumental in blocking the attempt.
"I knew the soldiers were going to agree because I had been named by Franco" and was their commander-in-chief, he said later. He knew most of the officers from his military training.
Although his blocking of the coup helped endear him to the nation, the king's image suffered in later years.
- Elephant-hunter -
The country had long closed its eyes to the numerous affairs the action-man king could boast.
But his decline began in 2012, when as a keen sportsman and hunter, he accepted a luxury elephant-hunting trip to Botswana, paid for by a Saudi entrepreneur, during a tough recession at home.
The trip, accompanied by his German mistress, came to light only because he broke his right hip and was flown home for surgery. The king made a public apology as he emerged from hospital on crutches.
His medical problems raised further questions over his reign.
Between May 2010 and November 2013, he had surgery nine times, including two operations on his right hip and three on his left.
Born in Rome on January 5, 1938, grandson of exiled king Alfonso XIII, Juan Carlos was just 10 years old when he was put on a train to Spain.
His father had agreed to have him educated under Franco in the hope of one day seeing himself sit on the throne.
Juan Carlos spent 27 years under the shadow of Franco, growing up in a series of military academies.
In May 1962 Juan Carlos married Sofia, a Greek princess. They were both keen sailors and had met on a cruise.
With Franco's blessing, the couple settled at the Zarzuela palace near Madrid and had three children: Elena, Cristina and Felipe, who as male heir bypassed his elder sisters to the throne.