Getty, Britain's leading patron of good causes, died in a London hospital where he was being treated for a chest infection.
Getty was admitted to the London Clinic on Monday for treatment of a recurrent infection but died Thursday morning, Dr. John Goldstone said.
"His family would like to extend their thanks to all those who have expressed their sympathy, which is greatly appreciated," Goldstone said in a statement.
During more than a quarter-century of living in Britain, the fiercely Anglophile Getty gave more than $200 million to many causes, including the National Gallery.
He once paid to rescue a family of seals caught in a storm, bought a mansion for needy children and gave a grand piano to a concert pianist who did not own one.
Getty was given the honorary title of Knight Commander of the Most Excellent Order of the British Empire in 1986 for services to charity, but could not be called Sir Paul then because he was not a British citizen.
He was invested with the full honors in 1998, a year after changing his citizenship.
"When I heard the national anthem played, I felt very proud to be British — it's my national anthem now," Getty said after his investiture at Buckingham Palace. "I love Britain's way of life. I love its people. I love its history and I love its future."
In 1985, he gave $63 million to the National Gallery in London. He also gave $32 million to the British Film Institute and millions more in smaller donations, often anonymous, to other charities and causes.
In a rare public statement after subsidizing the families of striking miners in 1985, Getty said he was "privileged to be the heir to huge wealth and I regard myself as custodian of that money for the benefit of people who need it more than I do."
John Paul Getty Jr. was born Sept. 7, 1932, the third of five sons of J. Paul Getty, nicknamed "Oklahoma Crude," who built Getty Oil into a $6 billion fortune — making him the richest man in the world in his day.
After attending the University of San Francisco and doing a brief stint in the army, Getty Jr. took charge of Getty Oil enterprises in Rome. But he resigned within six years, telling his father, "It doesn't take anything to be a businessman."
He then embarked on a freewheeling lifestyle of drugs and parties, growing his hair and adopting colorful velvet kaftans. In 1967, he divorced his wife of 11 years, Gail, with whom he had four children.
But the hippie life ended in 1971 when Getty's second wife, Bali-born model Talitha Pol, died of an accidental drug overdose in Rome.
He moved to Britain in 1972 and, for years, lived alone in a heavily secured mansion on the bank of the River Thames in London's upscale Chelsea neighborhood, taking solace in heroin and rum. He gave no interviews, issuing only the occasional statement through his lawyers.
The bulk of Getty's fortune came from a family trust after the sale of Getty Oil to Texaco in 1984. His father, from whom he was estranged, left him only a nominal sum in his will.
The younger Getty's fortune had been put as high as $2 billion, but he said much of it was in family trusts he did not control.
In 1971, Getty's teenage son from his first marriage, John Paul III, was abducted in Italy and held for five months. It was only after the kidnappers cut off part of his ear and sent it to the family that the boy's grandfather agreed to help pay a reported ransom of $3.4 million.
A year later, the youngster had a drug-induced stroke that left him a paraplegic and practically blind.
In 1994, the staunchly Catholic Getty married Victoria Holdsworth, his longtime British girlfriend, who is credited with his rehabilitation and gradual emergence into public life.
"I owe everything — repeat everything — to Victoria," he told an interviewer shortly after his marriage. "She has been my inspiration, you could say."