Mrs. Graham, who won a Pulitzer Prize in 1998 for her autobiography, Personal History, was attending an annual conference of business and media executives in Sun Valley, Idaho, when she fell on a concrete walkway outside a condominium.
President Bush paid tribute to Mrs. Graham, whom he called the "beloved first lady of Washington and American journalism."
In a statement, he said: "Mrs. Graham became a legend in her own lifetime because she was a true leader and a true lady, steely yet shy, powerful yet humble, known for her integrity and always gracious and generous to others."
Mrs. Graham's life story, as a soft-spoken and awkward debutante who through personal tragedy became one of the most towering figures in journalism and the first woman to head a Fortune 500 company, was as dramatic as it was inspirational.
Her father had bought the Post in 1933 and later turned it over to her husband, Philip L. Graham. When the dynamic but depressed Philip Graham committed suicide in 1963, Katharine Graham assumed control and did what both her father and husband failed to do - turned the mediocre Washington Post into an American institution.
"She set this paper on a course to excellence that you can't beat," Benjamin C. Bradlee, the Post's former executive editor, told CNN yesterday. "She was the most famous publisher of her day - not only the most famous, but the best."
As president and publisher of the Post during most of the politically turbulent 1970s, Mrs. Graham led the paper through historic decisions that lent it the authority to command sizable influence in the nation's capital.
Defying a court order and the advice of the newspaper's lawyers, she made the bold decision for the Post to print the Pentagon Papers, the government's secret chronicle of the Vietnam conflict.
Soon after, she bore the brunt of the fierce political pressure inflicted on the Post - pressure that included threats from the Nixon White House - during the Post's famous Watergate investigation.
The paper's investigation led to Richard M. Nixon's resignation and made the Post and Mrs. Graham - who would come to be known as the "iron lady" - powerful forces in newspaper journalism.
Arthur Ochs Sulzberger, chairman emeritus of the New York Times Co., said: "Throughout the last half of the 20th century, she used her intelligence, her courage and her wit to transform the landscape of American journalism, and everyone who cares about a free and impartial press will greatly miss her. We certainly will."
Even after turning the job of publisher over to her son Donald E. Graham in 1979, and then the chairmanship of the company in the early 1990s, Mrs. Graham was chairman of the Washington Post Co.'s executive committee and remained one of the capital's most famous and influential people.
Her elegant Georgetown home was the setting for some of the city's most power-packed parties, most recently a dinner for President Bush that was seen as the Texan's formal introduction to the town's power elite.
President Bill Clinton dined there after his 1992 election, and President Ronald Reagan was a guest of honor at her home twice.
Mrs. Graham once said that she had considered titling her autobiography Two Separate Lives because her lives before and after her husband's suicide - and her stewardship of the Post - were so vastly different.
Mr. Meyer was Jewish, but his children were baptized and raised Lutheran. In fact, Mrs. Graham said in her autobiography, growing up, "I was totally - incredibly - unaware of anti-Semitism, let alone of my father's being Jewish."
The Meyer family moved between homes in New York and Washington, but as Mrs. Graham described it in her autobiography, her life of privilege and wealth - private schools and horseback riding, music and French lessons, tutors and governesses, European travel and fabulous parties - was a lonely one.
Her father was difficult, her mother aloof, and her friends were intimidated by the formal atmosphere of her 40-room home in Washington, filled with Chippendale furniture and precious art and silent family dinners.
As a diversion in his retirement, Mr. Meyer bought the bankrupt Washington Post in 1933, using it to take aim at the New Deal.
Katharine Meyer, too, was interested in journalism. After attending Vassar College and the University of Chicago and working at The San Francisco News as a reporter, she went to work for her father at the Post as an editorial writer.
"If it doesn't work, we'll get rid of her," her father told Time magazine.
In 1939, she met Philip Graham, who was a Supreme Court law clerk and who, as Katharine Graham would write, captivated her immediately.
Upon his marriage proposal to Katharine, Philip Graham vowed never to accept help from the young heiress' father or to become involved with him in business. But after serving in the Army during World War II and as part of Franklin D. Roosevelt's inner circle, Mr. Graham agreed to join the Post as associate publisher.
After Mr. Meyer left the paper to head the World Bank, Philip Graham, whose liberal politics represented a sharp change from Mr. Meyer's, became publisher. The newspaper prospered under Philip Graham, who boosted circulation by acquiring the Post's chief competitor, The Washington Times-Herald. He also bought Newsweek magazine, giving the company a national profile.
What's more, Philip Graham had forged close ties with important political leaders. In 1960, he helped persuade John F. Kennedy to choose Mr. Graham's friend Lyndon B. Johnson as his running mate. Mr. Graham, unlike his wife who would succeed him, was not above allowing his personal politics to seep into the paper's political coverage.
For her part, Katharine Graham managed the couple's social and home life, raising four children - Elizabeth (known as "Lally"), Donald, William and Stephen - after losing her first son at birth.
But even in such a swirl of power, money and influence, she retreated, becoming increasingly withdrawn as her domineering husband belittled and ridiculed her, treating her like a "a second-class citizen" and a "doormat."
"I increasingly saw my role as the tail to his kite," she wrote.
Though she did not know it at the time, Philip Graham was manic-depressive. For years, she tried to hide his illness, even though it was accompanied by emotional breakdowns, tirades aimed at her and, in the end, an affair with a young Newsweek reporter.
When the young woman called one Christmas Eve, Katharine Graham picked up the phone just as her husband did in another room, and learned of the affair.
"That Christmas Eve afternoon," she wrote in a candid account of her marriage in her book, "the world I had known and loved ended for me."
Soon after, Philip Graham's condition deteriorated, and he entered a mental hospital. While at their country house in Virginia during a hospital leave, Philip Graham shot himself to death.
Racked by insecurity, she once said that, in taking over the newspaper, she felt pure "terror."
"Sometimes you don't really decide, you just move forward, and that is what I did - moved forward blindly and mindlessly into a new and unknown life."
But as the new president of the Post Co., she proved anything but a placeholder. She became a tough, principled and progressive leader and sought out the best journalistic talents of her times.
In 1965, believing the paper needed to be enlivened, she hired Mr. Bradlee, Newsweek's Washington bureau chief, who had been aggressively pursuing the job of Post managing editor.
"Part of me thought, 'What gall this guy has to be so pushy when he doesn't even have the job,'" she wrote. "But part of me thought, 'Maybe this is exactly what we need and what I'm looking for.'"
Mr. Bradlee went on to lead the editorial side of the newspaper as executive editor during its heyday in the 1970s.
In 1971, The New York Times obtained the Pentagon Papers, the government documents concerning the Vietnam War that Daniel Ellsberg, a former Defense Department official, had secretly leaked. A federal judge issued a restraining order against the Times. When the Post obtained its own copy of the documents, it was up to Mrs. Graham to decide whether to defy the court order and publish, as the newsroom recommended, or, as the lawyers advised, not publish.
"Frightened and tense, I took a big gulp and said, 'Go ahead, go ahead, go ahead. Let's go, let's publish,'" Mrs. Graham wrote.
In the end, the restraining order was lifted and the episode became a landmark First Amendment ruling by the Supreme Court.
For the news media and its advocates, the decisions by the Times and Post to publish the Pentagon Papers came to be seen as acts of courage on behalf of a free press.
Soon after, in June 1972, two young Post reporters, Bob Woodward and Carl Bernstein, started investigating a burglary at the Democratic Party headquarters at the Watergate complex.
The administration challenged license renewals for TV stations the Post owned. And for many months even some of Mrs. Graham's friends - and readers - doubted the central premise of the Watergate story: that a president and numerous close allies had taken part in a vast coverup as part of a pattern of crimes aimed at their perceived enemies.
"The credibility of the paper was on the line," Mr. Bernstein told CNN yesterday. "And she had the courage to go with two 28-year-old kids that she really didn't know."
The Post won a Pulitzer Prize for its Watergate coverage in 1973. The next summer, Mr. Nixon resigned.
Watergate catapulted the Post, and Mrs. Graham, to journalistic heights. At the same time, she was successfully tending the business side of the newspaper, turning the Post Co. into a profitable conglomerate of newspaper, magazine, broadcast and cable properties.
She raised money for expansion by taking the company public in 1971. And demonstrating her resolve as a businesswoman, she took on - and broke - the pressmen's union and several other labor units in 1975 after a violent five-month strike.
By the time she turned the mantle of president and CEO of the Post Co. over to her son Donald in 1991, it ranked 271st on the Fortune 500 list and was valued at nearly $2 billion. In 1993, Donald Graham succeeded his mother as company chairman, with Mrs. Graham becoming chairman of the company's executive committee.
Mrs. Graham, who spent Augusts at her home on Martha's Vineyard, had been working on a book about the history of Washington and still came to her office at the Post every day when in town.
Besides her son Donald, Mrs. Graham is survived by her daughter, Elizabeth Weymouth, a Post and Newsweek journalist, of New York; and her two other sons, William Graham, an investor, of Los Angeles; and Stephen Graham, a producer, philanthropist and doctoral student of English literature, of New York; 10 grandchildren and one great-grandchild; and her sister, Ruth M. Epstein of Bronxville, N.Y.
The funeral service will be at 11 a.m. Monday at the National Cathedral in Washington.