Aaron De Groft, the former director of the Orlando Museum of Art, who came to national prominence in 2022 after paintings he was exhibiting as the lost work of Jean-Michel Basquiat were seized by the F.B.I. as fakes, died on Saturday in Orlando. He was 59.

Kathryn Lee De Groft, his wife of 34 years, issued a statement saying he had died “after a brief illness.” No further information was available about the cause of death.

In February 2022, the Orlando Museum of Art opened a blockbuster exhibition of 25 paintings that Mr. Basquiat was said to have created in 1982, when he was 22 and living in Venice, Calif.

Mr. De Groft said that Mr. Basquiat had sold the artworks, most of them painted and drawn on slabs of cardboard, for $5,000 in cash, and that they had languished for decades in a Los Angeles storage unit. In 2012, Mr. De Groft said, the storage unit was foreclosed for lack of payment and the contents auctioned off. A little-known dealer purchased the artworks for about $15,000.

At the time of the exhibition, they were said to be worth nearly $100 million. Some museum staff members raised concerns about their authenticity but were rebuffed by the museum’s board chairwoman and threatened by Mr. De Groft with termination if they publicly aired their skepticism.

Days after the exhibit opened, The New York Times published an article raising questions about the paintings. The article noted doubts expressed by several curators, and reported that one of the paintings was made on a piece of cardboard shipping material containing a printed FedEx typeface not used by that company until 1994 — six years after Mr. Basquiat’s death and 12 years after Mr. De Groft and the painting’s owners said the painting was made.

The F.B.I. raided the museum four months later, confiscating all 25 works. An affidavit revealed that the bureau had been investigating the artworks and their owners for a decade.

A few days later, Mr. De Groft was fired.

The museum subsequently sued Mr. De Groft for fraud, saying the museum’s “99-year legacy was shattered.” The suit accused Mr. De Groft of seeking to profit from the future sale of the Basquiats after helping to authenticate and raise their value by exhibiting them.

Mr. De Groft continued to insist that the works were authentic. “I did my due diligence” he told The Times in 2023.

Aaron Herbert De Groft was born on Dec. 2, 1965, in Smithfield, Va., to Herbert De Groft, a Marine and later an executive with the Smithfield Packing Company, and Mary Ellen De Groft.

By his own admission, Mr. De Groft was a latecomer to the art world. As a boy, he was more likely to be found hunting game than haunting the library. He was recruited to play baseball by the College of William & Mary, and athletics and a career in the Major Leagues remained foremost for him — until his junior year, when a sports injury to his knee forced him to pivot.

“I couldn’t play baseball anymore,” he told Orlando’s Community Paper in 2021, but “I had no plan B.” He had been taking a few architecture classes and became enamored of art history. “So I hobbled over to what was the new art museum at the time,” the school’s Muscarelle Museum of Art, he said.

After graduating from William & Mary in 1988, he went on to earn a master’s degree from the University of South Carolina and a doctorate from Florida State University, both in art history.

In 1991, he married Kathryn Lee (Gardner) De Groft. She is the director of library and information services at Trinity Preparatory School in Winter Park, Fla. She survives him, as do their daughter, Ellie; a son, Graham; a brother, Jason; and his parents.

Mr. De Groft was hired as senior curator at the Cummer Museum of Art & Gardens in Jacksonville, Fla., and later became deputy director and chief curator at the John and Mable Ringling Museum of Art in Sarasota. He returned to William & Mary in 2005 as executive director of the Muscarelle with a newfound passion for sleuthing out an artwork’s provenance.

“I looked at the museum business as a detective business a lot of times,” he said, citing his own discerning eye and touting his ability to unearth masterpieces that were mistakenly attributed to lesser names — and therefore grossly undervalued.

When he was hired by the Orlando Museum of Art as director and chief executive in 2021, he promised to stage blockbuster shows and reap national attention. He delivered on that promise, but not quite in the way museum trustees had intended.

After the Basquiat exhibit was shut down, a Los Angeles auctioneer admitted to the F.B.I. that he had helped create the faux Basquiats in 2012, some in as little as five minutes.

Mr. De Groft countersued the museum for wrongful termination, calling their claims a “public relations stunt intended to save face.” He still insisted that the Basquiats were genuine.

He said the artworks’ owners had commissioned a forensic investigation by a handwriting expert, who identified the signatures on many of the paintings as being Mr. Basquiat’s. He also cited an analysis by a Basquiat expert — since disavowed — and statements by a member of the Basquiat estate’s now-defunct authentication committee, who found the paintings to be genuine.

Mr. De Groft said he was furious that his professional reputation had “been trashed for doing nothing wrong.” He promised he would be vindicated in court. A trial in Orlando was scheduled to begin in October. “I’m fighting back,” he said in the 2023 interview. “I’m going to war.”

The Orlando Museum of Art issued a statement on Monday saying it was “saddened to hear about the passing of Dr. Aaron De Groft.” Its current director, Cathryn Mattson, did not respond to a request for comment on whether the lawsuit would continue against Mr. De Groft’s estate. She told The Orlando Sentinel that the museum’s board and its lawyers would meet to “consider options.”

Robert Parks, the attorney for Mr. De Groft, did not immediately respond to a request for comment on the future of his client’s countersuit against the museum, though he told The Sentinel that it was too soon for the De Groft family to make a decision about proceeding.

The F.B.I.’s Art Crime Team has said that its criminal investigation regarding the now-notorious fake Basquiats — all still held by the F.B.I. — is continuing.