Alberto W. Vilar, a money manager with a love of opera who used his wealth to become a conspicuous arts patron but fell out of favor when he reneged on his pledges and eventually went to prison for defrauding clients, died on Saturday at his home in Queens. He was 80.

His sister and only immediate survivor, Carole Vilar Williams, said the cause was a heart attack.

Mr. Vilar built his fortune — once estimated at nearly $1 billion by Forbes magazine — through Amerindo Investment Advisors, a firm he co-founded that focused on biotechnology and technology stocks. He used those riches to embark on a run of largess in the 1990s and early 2000s, donating — or pledging to donate — more than $200 million to arts organizations.

For his $25 million pledge to the Metropolitan Opera’s endowment in 1998, Mr. Vilar’s name was added to its third-level Grand Tier. (He also had a seat on the Met’s board.) For his $18 million pledge to the Royal Opera House in London in 1999, its Floral Hall became the Vilar Floral Hall. For his $50 million pledge to the Kennedy Center for the Performing Arts in Washington in 2001, the center planned to fund annual visits by the Kirov Ballet and Opera and to establish the Vilar Institute for Arts Management.

“He was not — how shall I say? — quiet about his giving,” Beverly Sills, the soprano and former Met chairwoman, told The New York Times in 2005. “I think that was a turnoff for other members of the board, the fact that he wanted more attention.”

But Mr. Vilar defended his propensity for exchanging donations for naming rights, telling The Times in 2000: “When you have your name on a building, it says, ‘Here’s a world-class person who is giving money, and he chose us.’ Isn’t that a message?”

His time as a modern Medici, however, lasted only as long as the technology market continued to boom. In 1999, his Amerindo Technology Fund posted a return of 249 percent. But the fund’s return fell by 64.8 percent in 2000, 50.8 percent in 2001 and 31 percent in 2002. He began to fail to make payments on his pledges, like the 1998 one to the Met, others to the Washington and Los Angeles Operas and another to the Lyric Opera of Chicago.

Many of his recipients, frustrated when the checks never arrived, removed his name from places of honor, a rare and humiliating occurrence in the genteel world of arts philanthropy. Gone were the foot-high metal letters from a wall on the Met’s Grand Tier. Menu covers with his name in the Grand Tier restaurant were tossed out. “Vilar” was taken off the Floral Hall at Covent Garden. He paid only a sliver of his promised donation to the Kennedy Center.

It all ended for Mr. Vilar in May 2005, when he was arrested and subsequently indicted on federal fraud and money-laundering charges that centered on the misuse of millions of dollars invested with Amerindo by several clients. According to the indictment, Mr. Vilar in 2002 told one client, Lily Cates, that her $5 million was to be invested in a government-backed fund intended to attract venture capital to small businesses.

But he never received government approval for the fund, and deposited Ms. Cates’s money in the brokerage account of an Amerindo entity in Panama. Soon, $1 million of the money was wired to an account of Mr. Vilar’s at Chase Manhattan Bank. He quickly used the money to fulfill pledges to his alma mater, Washington & Jefferson College in Pennsylvania, and to the American Academy in Berlin, and to pay bills from a caterer and a dishwasher repair service.

Another $3.1 million was wired from the Panama account to a financial institution in Luxembourg. The complaint said that Mr. Vilar had then funneled the last of Ms. Cates’s investment into personal and offshore accounts.

Before his trial began in 2008, Mr. Vilar said that the government would not be able to prove its case.

“She made millions with the firm, and I had complete authorization to invest her money,” he told The Times, referring to Ms. Cates, the mother of the actress Phoebe Cates. He said she later “got a bee in her bonnet about something” and asked that her money be returned.

“Next thing I know,” he added, “she files a complaint that we had stolen her money.”

Prosecutors argued that Amerindo had gambled with clients’ money in volatile technology stocks instead of the safe investments they had been promised. A jury found Mr. Vilar guilty on all 12 counts that he faced. It found his former partner in Amerindo, Gary A. Tanaka, guilty on three counts.

In 2010, Judge Richard Sullivan of U.S. District Court in Manhattan sentenced Mr. Vilar to nine years in prison.

“You made use of investors’ assets as if they were your own,” he told Mr. Vilar at the sentencing. “This kind of behavior just can’t be tolerated.”

Albert William Vilar Jr. was born on Oct. 4, 1940, in East Orange, N.J. (not Havana, as he sometimes claimed). Albert Sr. was a Cuban-born executive of a sugar company that had offices in Manhattan and Puerto Rico. His mother, Margaret (Walsh) Vilar, was a homemaker.

Mr. Vilar told The New Yorker in 2006 that he and his family moved to Puerto Rico when he was 7 and that he had attended grade school and high school there. He backed off claims that he had lived in Cuba and that his family had fled after Fidel Castro came to power.

As a boy, Albert Jr. (who added an ‘o’ to his given name during his business career) was fascinated by classical music, but his dreams of being a conductor were discouraged by his father, he said. He studied economics at Washington & Jefferson. After two years in the Army, he worked at Citibank and Boston Company, an investment management firm, then as a money manager in Kuwait.

He and Mr. Tanaka started Amerindo in the 1980s. At its peak, the firm managed as much as $10 billion for a broad swath of clients.

Mr. Vilar’s wealth afforded him an opulent lifestyle. He owned several homes, including a 25th-floor luxury duplex condominium at the United Nations Plaza overlooking the East River. It had a Steinway baby grand piano, a bronze statue of the child Mozart with a violin, miniature facsimiles of the Met’s crystal chandeliers hanging above his dining room table, and frescoes that were copies of the rococo paintings in Salzburg’s Mozarteum concert hall. He said he had planned to build a 70-seat auditorium for musical performances on the floor below.

Mr. Vilar was proud of his front-row seat at the Met — A101. And he did give away substantial amounts. When his funds were still reaping big returns, he donated $11.8 million to the Met between 1990 and 2002, largely to pay for productions of “Cosi fan tutte,” “Fidelio,” “La Traviata,” “Le Nozze di Figaro” and “La Cenerentola.”

He lost an appeal of his conviction in 2013. The next year, Judge Sullivan added a year to his sentence, saying that Mr. Vilar and Mr. Tanaka had taken actions to prevent victims of his crimes from being repaid.

After his release from prison in 2018, Mr. Vilar lived on Social Security in his Queens apartment. His sister said that he had been writing his autobiography.

His lawyer, Vivian Shevitz, said that Mr. Vilar had hoped that the government would release frozen Amerindo monies so that he could collect a pension.