He died Sunday evening at a Pittsburgh hospital while awaiting cardiac surgery, according to a statement from his company.
With his dominance in golf and distinctive style, Palmer helped turn the sport from a country club pursuit to one that became accessible to the masses.
He won more than 90 golf tournaments, including the Masters four times, the U.S. Open in 1960, and the British Open in 1961 and 1962.
Palmer became the first person to make $1 million playing golf.
"I would like to be remembered for bringing golf to a worldwide audience," he told CNN in 2012. "Players today have no boundaries."
He and his two great rivals in the "Big Three" -- Gary Player and Jack Nicklaus -- helped take the sport around the globe in the 1960s, capitalizing on the ever-growing reach of television. Golf grew into made-for-television events and with it came massive sponsorship and prize money.
"He took the game from one level to a higher level, virtually by himself," wrote Nicklaus in a statement.
"Arnold always had my back, and I had his. We were always there for each other. That never changed. He was the king of our sport and always will be."
After learning to play golf at age 4, Palmer never stopped.
Winning in style too
It was not only Palmer's knack for golf that won him legions of adoring fans.
Long before the age of social media, Palmer was the first golfer to attract his own special following -- "Arnie's Army" -- diehard fans who surrounded every green to cheer him on, win or lose.
"When I was a boy learning to play golf in my hometown of Latrobe, Pennsylvania, I never could have imagined that one day I'd have an 'Army' of fans or that people would call me 'The King' of the sport I love," Palmer previously wrote on his website.
He had charisma combined with good looks and style.
GQ Magazine named him one of the "50 most stylish men of the past 50 years" and Esquire had him in a list of the "75 best-dressed men of all time."
Golfers are rarely remembered for their fashion sense, usually the exact opposite. But Palmer insisted on a consistent style throughout his career.
"It was not something I really planned," he told CNN in 2012. "I liked a sharp crease in my slacks, my shoes polished to shine, while my shirts were conservative with a straight collar."
Palmer even had a drink named after him -- a mix of lemonade and iced tea that he used to take on the golf course with him in a thermos.
Born in Latrobe, Pennsylvania, he was taught how to play the game by his father who worked at the local country club.
Palmer started his professional career in 1954 after winning the United States Golf Association Amateur Championship.
Two years later he signed with Mark McCormack, who founded what would become the global sports management behemoth International Management Group (IMG). The late McCormack promoted Palmer, who proved to be a very marketable star, showing that an athlete's commercial endorsements could outstrip prize-money earnings.
Palmer retired from competitive golf in 2006, but remained active in the sport.
"It is not an exaggeration to say there would be no modern day PGA TOUR without Arnold Palmer," said PGA TOUR Commissioner Tim Finchem in a statement. "There would be no PGA TOUR Champions without Arnold Palmer. There would be no Golf Channel without Arnold Palmer. No one has had a greater impact on those who play our great sport or who are touched by it."
A PGA tour competition was renamed for Palmer, in 2007. The Arnold Palmer Invitational is played every March in Orlando.
Tiger Woods tweeted: "It's hard to imagine golf without you or anyone more important to the game than the King."
Palmer received the Presidential Medal of Freedom in 2004 and the Congressional Gold Medal in 2012.
Former President George W. Bush, who presented him the Presidential Medal in 2004, said in a statement: "He was a great American whose friendship - and swing thoughts - will be missed."
Palmer is survived by his second wife, Kit, his two daughters, six grandchildren and many great-grandchildren.