T. Boone Pickens, the legendary Texas oil magnate, philanthropist and hedge fund founder, died Wednesday. He was 91. 

Spokesman Jay Rosser said that Pickens died of natural causes, after health issues such as multiple strokes in recent years.

Pickens, who said he was worth $950 million in 2013, was called the "Oracle of Oil" due to his long career in oil and gas. After a period as a wildcatter in the 1950's at Phillips Petroleum, Pickens started an energy company that later became Mesa Petroleum, which grew to be one of the largest independent oil companies in the world by the early 1980s.

In the 1980s, Pickens rose to fame as a corporate raider, with Pickens saying in a 2017 Forbes column that he was a "disrupter before disrupters were cool." He made hostile bids to take control of major oil companies such as Gulf Oil, Phillips and Unocal.

He criticized the leadership of these companies and would become richer by selling his shares back to the companies when he gave up his takeover attempts, which is a practice known as "greenmail."

He founded the hedge fund BP Capital Management in 1996 after leaving Mesa Petroleum. He then formed the Pickens Fuel Corporation a year later and sought to promote natural gas over oil. 

Pickens closed BP Capital Management in 2018 due to poor profitability and his personal health issues. 

Pickens also donated to numerous Republican politicians, such as former President George W. Bush. Pickens had promoted the Pickens Plan in 2008, a strategy that would make the United States energy independent by investing in wind turbines and shifting the way the country uses natural gas. 

As a philanthropist, Pickens often gave millions to Oklahoma State University, his alma mater. The university even named its renovated football stadium after him. He also signed on to the Giving Pledge, a commitment to give half of his net worth to charity. 

Pickens was married five times and has five children. 

Former Oklahoma Sen. Tom Coburn said that Pickens "is one of the swashbucklers of our history – a great, dynamic person who is a pioneer in multiple areas. He was a visionary. There are not many of those anymore. He was probably little influenced by power and money."