Scaife died early Friday at his home, his newspaper, the Pittsburgh Tribune-Review, reported. Scaife's death comes less than two months after he announced in a first-person, front-page story in his Pittsburgh Tribune-Review that he had an untreatable form of cancer.
"Some who dislike me may rejoice at the news," wrote Scaife, who acknowledged making political and other enemies. "Naturally, I can't share their enthusiasm."
He was the grand-nephew of Andrew Mellon, a banker and secretary of the Treasury who was involved with some of the biggest industrial companies of the early 20th century. Forbes magazine estimated Scaife's net worth in 2013 at $1.4 billion.
The intensely private Scaife became widely known in the 1990s when first lady Hillary Rodham Clinton said her husband was being attacked by a "vast right-wing conspiracy." White House staffers and other supporters suggested Scaife was playing a central role in the attack.
Several foundations controlled by Scaife gave millions of dollars to organizations run by critics of Clinton, including $1.7 million for a project at the conservative American Spectator magazine to dig up information about his role in the Whitewater real estate scandal.
Scaife rarely gave interviews, but in a sit-down with George magazine editor John F. Kennedy Jr. in 1998, he called President Clinton "an embarrassment."
In the interview, Scaife denied that his money helped support an effort to hurt the president, but he suggested Clinton might be linked to the deaths of dozens of administration officials and associates, including White House Deputy Counsel Vince Foster and onetime Commerce Secretary Ron Brown. Foster's death was determined to be a suicide; Brown died in a plane crash.
Scaife also accused Kenneth Starr, the independent counsel whose investigation led to Clinton's impeachment in the Monica Lewinsky sex scandal, to be a "mole working for the Democrats."
Scaife's stance toward the Clintons softened years later. In an interview published in early 2008, he told Vanity Fair magazine he and the former president had a "very pleasant" lunch the previous summer, and "I never met such a charismatic man in my whole life."
Clinton gave Scaife an autographed copy of his book, and Scaife said he later sent $100,000 to the Clinton Global Initiative. (Scaife also said philandering "is something that Bill Clinton and I have in common.")
Scaife's newspaper also endorsed Hillary Rodham Clinton's bid for president in 2008.
Despite funding many causes dear to conservatives, Scaife was libertarian on many social issues. He supported Planned Parenthood and abortion rights, supported legalizing same-sex marriage and marijuana, and opposed the invasion of Iraq in 2003.
Scaife bought the Tribune-Review in suburban Pittsburgh in 1969, using its editorial pages to trumpet his views.
"I fell in love with newspapers as a boy, when my father bought me editions from around the country and abroad," Scaife told readers in the column announcing his cancer diagnosis. "The day I became a newspaper publisher, buying the Tribune-Review, remains one of the proudest, happiest moments of my life."
Scaife was a longtime supporter of Republicans, backing presidential candidate Barry Goldwater in 1964 and heavily funding the 1968 campaign of Richard Nixon.
In 1972, Scaife donated $1 million to Nixon in 334 separate checks to avoid paying gift taxes. After The Associated Press wrote a story about the money, Scaife insisted the Tribune-Review get rid of its AP service.
"He ordered us to come in and take out the wire machines that night," Pat Minarcin, then AP's Pittsburgh bureau chief, told The Wall Street Journal for a 1995 story.
Scaife also made headlines in recent years during a bitter divorce battle with Margaret Ritchie Battle Scaife, his second wife. The divorce was finalized in 2012. His first marriage, to Frances Gilmore Scaife, also ended in divorce.
A Pittsburgh native, Richard Mellon Scaife was born in 1932, the son of Sarah Cordelia Mellon and Alan Magee Scaife. His mother was an alcoholic, and his upbringing has been described as cold and unhappy. He and his sister were raised by nannies.
He went to Yale but was expelled during his freshman year after a he rolled a beer keg down a flight of stairs, breaking the legs of a classmate, according to a 1999 story in The Washington Post.
Scaife admitted to becoming an alcoholic, and he had a reputation for having a fiery temper. He reportedly quit drinking in 1990 after going to the Betty Ford Clinic.
The Tribune-Review reported Scaife is survived by a daughter, Jennie K. Scaife, a son, David N. Scaife, a daughter-in-law, Sara Scaife; and two grandchildren.
The newspaper reported that a private memorial service would be held at a later date.