Van Cliburn, the tall, gangly, curly-haired Texan who became the most famous classical pianist in American history during a single extraordinary week in 1958, died Thursday at home in Fort Worth, Texas. He was 78.

His death, from bone cancer, was announced by publicist and longtime friend Mary Lou Falcone.

In April 1958, Mr. Cliburn went to Moscow at the height of the Cold War and brought home the gold medal in the new Tchaikovsky International Piano Competition for his rendition of the composer’s Concerto No. 1. The contest had been established to showcase the Russian superiority in culture, six months after the scientific triumph of launching Sputnik, the first space satellite.

Mr. Cliburn’s performance prompted an eight-minute standing ovation. But such were the political tensions of the time, the judges of the competition checked with Soviet Premier Nikita Khrushchev before announcing their decision to give the prize to a non-Soviet musician.

Save 75% on a Digital Subscription Today

“Is he the best?” Khrushchev is said to have replied. “Then give him the prize!”

Mr. Cliburn was mobbed in Moscow by admirers. Women reportedly wept and fainted at his concerts.

“Van looked and played like some kind of angel,” the Russian pianist Andrei Gavrilov later recalled. “He didn’t fit the evil image of capitalists that had been painted for us by the Soviet government.”

Mr. Cliburn was equally positive about the people he met during his visit.

“I was just so involved with the sweet and friendly people who were so passionate about music,” he later recalled. “They reminded me of Texans.”

His achievement was reported on the front pages of newspapers throughout the world. He returned home to a New York ticker-tape parade and the sort of shrieking, unfettered adulation that a few years later would be transmuted into Beatlemania. In May 1958, Time magazine put him on its cover with a banner that read “The Texan Who Conquered Russia.”

Fans ripped off the door of his limousine during a visit to Philadelphia. RCA Victor signed him to an exclusive contract, and his first recording — the Tchaikovsky Piano Concerto No. 1, of course — quickly became the best-selling classical record in history, a position it would retain for most of a decade.

By the time he was 24, he was the subject of a biography, “The Van Cliburn Legend.” Few young musicians have ever faced so many expectations.

Such sudden celebrity was heady stuff for a shy, soft-spoken man who not long before had spent most of his time playing scales in a practice room at New York’s Juilliard School. Not surprisingly, Mr. Cliburn seems to have found the expectations impossible to live up to. Within five years, his playing had begun a marked deterioration.

“From the mid-1960s, it seemed he could not cope with the loss of freshness,” Michael Steinberg wrote in the New Grove Dictionary of Music and Musicians. “His repertory was restricted; his playing, always guided primarily by intuition, took on affectations and the sound itself became harsher.”

By 1978, he had withdrawn from the concert stage. He moved to Fort Worth, where he bought a mansion and became increasingly prominent in the city’s social life. In 1989, he came out of retirement to play his signature piece at the Mann Center in Philadelphia, to respectful reviews.

After that, he made sporadic public appearances, almost always playing the Tchaikovsky, and usually on occasions when the principal interest was extra-musical — at the White House, say, or in a benefit for the Humane Society at the Kennedy Center.

“I do play concerts from time to time,” he told The New York Times in 2008. “I work at home quietly, go to the opera, hear concerts, see friends. I like making up now for what I was not able to have then.”

In later life, whenever he deigned to play, he sounded very much like what he was: a supremely gifted pianist who had not taken the pursuit especially seriously in decades.

At the Kennedy Center in 2004, he hit all sorts of wrong notes; he lost his place completely in Brahms’s Rhapsody in B minor and scurried around furtively until he found the right musical exit.

Much of his attention in later life was devoted to an American competition, modeled on the Tchaikovsky International, that bore Mr. Cliburn’s name and drew pianists from around the world to Fort Worth every four years. It remains the wealthiest, if not always the most esteemed, piano competition in the United States.

In the mid-1990s, Mr. Cliburn was briefly in the news after his former domestic partner Thomas Zaremba, a mortician who was also responsible for the pianist’s makeup, sued him for “palimony,” claiming he had managed Mr. Cliburn’s business affairs, paid bills and generally run the household from 1964 to 1994.

Mr. Cliburn’s attorneys countered that Zaremba was owed no community property because Texas law recognized no spousal relationships other than heterosexual unions. In 1997, the case was thrown out. Survivors, according to the announcement from Falcone, include his longtime friend Thomas Smith.