T. Boone Pickens, the famed oil prospector, hedge-fund founder, and billionaire philanthropist, died on Wednesday at 91, according to his website.

The "Oracle of Oil" profited from several buyout efforts — many of which were failures — as his Mesa Petroleum business sought to expand its footprint through the 1980s.

Pickens pivoted from oil in the 1990s and 2000s as he promoted natural gas as an alternative to gasoline and spent $100 million on a campaign for US energy independence.

The Oklahoma native was a major donor to prominent Republicans, backing President Donald Trump and former President George W. Bush.

T. Boone Pickens, the famed oil prospector, hedge-fund founder, and billionaire philanthropist, died on Wednesday at 91, according to his website.

Pickens founded the oil and gas company Mesa Petroleum and took it public in 1964. The company became one of the largest in the sector.

In the following decades, Pickens made several attempts to acquire larger oil companies like Gulf Oil, Phillips Petroleum, and Cities Service in a bid to grow his Mesa empire. Even when he'd lose a bidding war to a different company, Pickens often profited on the buyout attempt.

"Pickens and his young band of hungry Mesa Petroleum managers grabbed hold of a monster and shook it like it'd never been jostled before," a statement on his website said. "They rode that monster, and got thrown some, but Big Oil was never the same again."

The so-called Oracle of Oil later became a champion of the "shareholders rights" movement, founding the United Shareholders Association in 1986. He repeatedly called for corporate executives to find ways to benefit their stockholders. He called himself "a disrupter before disrupters were cool" in a 2017 Forbes column.

In 1996, at age 68, Pickens sold Mesa and started his hedge fund, BP Capital Management. He formed the Pickens Fuel Corp. a year later to promote the use of natural gas over gasoline, and spent $100 million in 2007 to launch a campaign for US energy independence.

The native of Holdenville, Oklahoma, was also among the biggest Republican donors of the past several decades. He supported George W. Bush in his gubernatorial and presidential races and backed Rudy Giuliani's 2008 presidential campaign and Donald Trump's bid for office in 2016.

Pickens also donated much of his wealth to other organizations, including the University of Texas Southwestern Medical Center and Oklahoma State University. The latter institution received a $165 million donation from Pickens in 2005 and ended up naming its renovated football stadium after him.

Pickens closed BP at the start of 2018 because of his declining health. He'd had a serious fall and numerous strokes in 2017.

"There's a story I tell about the geologist who fell off a 10-story building. When he blew past the fifth floor he thought to himself, 'So far so good,'" Pickens wrote in a July 2017 LinkedIn post. "That's the way to approach life. Be the eternal optimist who is excited to see what the next decade will bring."