Van Cliburn, the tall, gangly, curly-haired Texan who became the most famous classical pianist in American history over the course of a single extraordinary week in 1958, died Feb. 27 at his home in Fort Worth. He was 78.

His death, from bone cancer, was announced by his 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 Russian cultural superiority, a mere six months after the scientific triumph of launching Sputnik, the first space satellite.

Mr. Cliburn’s performance — the crystalline touch, the welling songfulness — 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.

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

Mr. Cliburn was mobbed in Moscow by joyful 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.”

Mr. Cliburn’s 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, by the critic and composer Abram Chasins, titled “The Van Cliburn Legend.” Few young classical musicians have ever faced so many expectations.

Such sudden celebrity was heady stuff for a shy, soft-spoken young man who not long before had spent most of his time playing scales in the obscurity of 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, Mr. Cliburn 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.

He “projected” so loudly that he sometimes came perilously close to banging; an author who wrote as Mr. Cliburn played would use mostly capital letters and refuse to break his paragraphs. And yet there were always transcendent moments, even in his weakest performances.

In person, Mr. Cliburn was gracious, courteous and spectacularly elusive. 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.

Of all the winners, only Radu Lupu (1966) went on to a great career, and it was often charged that the Cliburn “losers” were more interesting musicians than the ones who took top honors. The American critic Joseph Horowitz explored this phenomenon in detail in his 1990 book “The Ivory Trade: Music and the Business of Music at the Van Cliburn International Piano Competition.”

Mr. Cliburn distanced himself from any sort of judicial role in his competition. “I couldn’t do it,” he told the Times in 2008. “I’ve never been on a jury. It would be the hardest thing ever for me to do. I’m too understanding of why a person did a passage this way instead of that way.”

Harvey Lavan Cliburn Jr. was born in Shreveport, La., on July 12, 1934, and grew up in Kilgore, Tex. He was the only child of Harvey Lavan Cliburn, an oil executive, and the former Rildia Bee O’Bryan, a piano teacher.

His mother doted on him; with the exception of a couple of years in his 20s, they would live together until her death in 1994 at the age of 97. His mother started him on the piano when he was 3.

“When she gave the first prelude and fugue of Bach, she made me sing the theme,” he told the Dallas Morning News in 2008. “She wanted me to feel the connection with the human voice, because it is the first instrument.” He later studied in New York at the Juilliard School with the legendary pedagogue Rosina Lhevinne before graduating in 1954.

After early performances in Louisiana and Texas, Mr. Cliburn made his formal debut with the Houston Symphony Orchestra in 1954, playing what would be his lifetime signature piece, the Tchaikovsky first piano concerto. He made his New York debut with the New York Philharmonic in November 1954.

Music critic Irving Kolodin, writing in the Saturday Review, called him “the most talented newcomer of the season. . . . He literally commands the piano as he plays and in many ways the music, too. . . . He has, in abundance, the qualities of fervor, audience appeal and musicianship which make for distinction.”

Mr. Cliburn was hardly a novice when he went to Russia in April 1958; he was 23 and had won several important American competitions. But musical accomplishment is no guarantee of fame and fortune (or, for that matter, even of a living wage), and Mr. Cliburn had already given up his New York apartment to move back in with his parents in Kilgore. The decision to go to Russia was something of a last chance, and it paid off for the rest of his life.

In Mr. Cliburn’s early years, he was a splendid artist, with a technique that knew no difficulties. His early recordings — not only heroic concertos but solo albums devoted to Brahms, Chopin and Debussy — all testify to the power and poetry of his playing.

But he relinquished his crown while he was still a young man, and his life may be seen as a long study in anticlimax.

In the mid-1990s, Mr. Cliburn was briefly in the news after his former domestic partner Thomas E. Zaremba, a mortician who was also responsible for the pianist’s makeup, sued him for palimony, alleging that 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 because Texas law recognized no spousal relationships other than heterosexual unions, Zaremba was owed no community property. In 1997, the case was thrown out.

Survivors, according to the announcement from Falcone, include a friend of long standing, Thomas L. Smith.

In the denouement of his life, Mr. Cliburn was showered with awards. He received the Kennedy Center Honors in 2001, and in 2010 President Obama presented him with the National Medal of Arts at the White House.

“Since his historic 1958 victory at the first International Tchaikovsky Competition in Moscow, Mr. Cliburn has reached across political frontiers with the universal message of beautiful music,” Obama said.

Mr. Cliburn later called the event “a lovely service.”

“They were so nice, very sweet, very kind. I was so thrilled,” he told the Fort Worth Star-Telegram. He was then asked how many presidents he had played for.

“Every one, every one since Eisenhower,” Mr. Cliburn replied.

None of this could have been predicted while Mr. Cliburn was growing up in small-town Texas.

“I remember calling my mother from Russia and telling her I’d won the competition,” he told this reporter in 1989. “I had no idea that the story had become so big. So I asked her if she’d told Mrs. So-and-So across town that I’d won. And she said yes, she knew all about it. And I asked her if she’d told Mr. So-and-So in the next town over that I’d won. And she said, yes, he knew about it, too. And I felt pretty good, because it was all very well to be known in your town, but what really mattered was if your reputation had spread to the next town. Then you’d really made it.”

He smiled and shook his head.

“I was mighty proud that night,” he said, a touch of awe in his voice.