The blue-eyed star of films like Butch Cassidy And The Sundance Kid had died at home on Friday surrounded by family and close friends, said Jeff Sanderson.
Newman was nominated for an Oscar 10 times, winning the best actor trophy in 1987 for The Color Of Money.
In May 2007, he said he was giving up acting because he could no longer perform to the best of his ability.
"I'm not able to work any more... at the level that I would want to," he told US broadcaster ABC.
"You start to lose your memory, you start to lose your confidence, you start to lose your invention.
"So I think that's pretty much a closed book for me."
Earlier this year, he pulled out of directing a stage production of John Steinbeck's Of Mice and Men in Connecticut because of unspecified health problems.
Broadcaster Sir Michael Parkinson, who interviewed Newman for a documentary, said the star had been "a real giant of the cinema".
"He was the link between the great time of Hollywood, the Cary Grant and people like that, and Tom Cruise," he told BBC News.
"He fills the gap between the two, and fills it in a most extraordinary, dominant manner."
Although his handsome looks and piercing blue eyes made him an ideal romantic lead, Newman often played rebels, tough guys and losers.
"I was always a character actor," he once said. "I just looked like Little Red Riding Hood."
He appeared in some 60 movies, including Cat On A Hot Tin Roof, The Hustler, The Sting and Hud.
Along the way, he worked with some of the biggest names in Hollywood - including Alfred Hitchcock, Robert Altman, Martin Scorsese, Elizabeth Taylor, Lauren Bacall and Tom Hanks.
He also appeared with his wife, Joanne Woodward, in several films including Long Hot Summer and Paris Blues. The star later directed his wife in movies such as Rachel, Rachel and The Glass Menagerie.
But his most famous screen partner was undoubtedly Robert Redford, his sidekick in both Butch Cassidy and The Sting.
In addition to his Academy Award for best actor, he was given an honorary Oscar in 1986 "in recognition of his many and memorable compelling screen performances and for his personal integrity and dedication to his craft".
In 1994, he won a third Oscar, the Jean Hersholt Humanitarian Award, for his charitable work.
His philanthropic efforts included the establishment of summer camps for children who suffered from life-threatening illnesses.
He also donated profits from his Newman's Own food range to a number of charitable organisations.
Newman's last film role was as the voice of Doc Hudson, one of the most famous racing cars in history, in the Pixar animation Cars.
It was perhaps a fitting epitaph for the actor, who had a lifelong fascination with the sport - and put his film career on hold in the 1970s to become a professional racing driver.
He is survived by his wife, five children, two grandsons and his older brother Arthur.