Texan billionaire Ross Perot, who in the 1990s twice ran for US president against candidates from the two main parties, has died at the age of 89.
Described as idiosyncratic and feisty, he pioneered the computer data industry by founding his own company in 1962.
But he was best known for running in the 1992 campaign, advocating balanced budgets and calling for an end to the outsourcing of jobs abroad.
Perot took almost a fifth of the popular vote in the three-way race.
That made him one of the most successful independent candidates in US history, and was believed to have helped Democrat Bill Clinton defeat incumbent George HW Bush.
Perot ran for president again in 1996, after forming the Reform Party.
He was diagnosed with leukaemia earlier this year.
H Ross Perot was an American original. A self-made billionaire with a penchant for plain-speaking in his clipped north Texas twang, he built a reputation as a savvy technology entrepreneur and spent a small fortune helping US veterans and attempting to free American hostages abroad.
He was also a political harbinger.
His 1992 independent presidential bid - the most successful third-party candidacy in eight decades - exposed fault lines in the US political system that would someday result in electoral earthquakes. He capitalised on the thirst of American voters for an outsider who could disrupt two-party government and built a dedicated following with his populist, small-government, anti-trade, anti-globalist rhetoric.
His unconventional candidacy, announced on a US talk show, straddled the line between entertainment and politics and contributed to the defeat of incumbent Republican President George HW Bush.
Although his second presidential bid in 1996 faltered and the Reform Party he founded crumbled once he scaled back his involvement, the ideological themes he built it on would later be adopted by Donald Trump to bring the establishment of the Republican Party as it existed for decades crashing down.
The Perot family said in a statement on Tuesday: "Ross Perot, the ground-breaking businessman and loving husband, brother, father and grandfather, passed away early Tuesday at his home in Dallas, surrounded by his devoted family."
Reacting to the news, Vice-President Mike Pence said Perot had been "a great American, a true patriot and a steadfast supporter of our military".
Bill Clinton said: "Although we were opponents in 1992 and 1996, I respected Ross for his support for our veterans, the business he built, and the passion he brought to his politics."
Born in 1930, during the Great Depression, Perot grew up in poverty. He began his technology career working in sales for IBM, before founding Electronic Data Systems (EDS) in 1962, at the age of 32.
The company - which was later sold to Hewlett-Packard - made him rich. In the 1980s he set up Perot Systems which was eventually acquired by Dell for $3.9bn.
As an employer, Perot was known for his quirks - particularly his strict dress code. Workers had to wear white shirts and ties, and beards were banned.
When two of his employees were jailed in Iran in 1979 over a contract dispute - just before the Islamic Revolution - he financed a private commando rescue in a raid that inspired a book and a film.
He championed patriotic causes, and in the late 1970s and 1980s claimed that hundreds of missing US soldiers had been left behind and imprisoned after the Vietnam War.
The 1992 campaign - during which Perot spent $63m (£50m) of his own money - made him a household name. At one point in June that year, he had a lead over both his mainstream rivals. Perot finished a strong third in the November election.
His second campaign in 1996 was less successful. He did not take part in presidential debates and got just 8% of the vote.