Paul G. Allen, the co-founder of Microsoft who helped usher in the personal computing revolution and then channeled his enormous fortune into transforming Seattle into a cultural destination, died on Monday in Seattle. He was 65.
The cause was complications of non-Hodgkin’s lymphoma, his family said in a statement.
The disease recurred recently after having been in remission for years. He left Microsoft in the early 1980s, after the cancer first appeared, and, using his enormous wealth, went on to make a powerful impact on Seattle life through his philanthropy and his ownership of the N.F.L. team there, ensuring that it would remain in the city.
Mr. Allen was a force at Microsoft during its first seven years, along with its co-founder, Bill Gates, as the personal computer was moving from a hobbyist curiosity to a mainstream technology, used by both businesses and consumers.
When the company was founded, in 1975, the machines were known as microcomputers, to distinguish the desktop computers from the hulking machines of the day. Mr. Allen came up with the name Micro-Soft, an apt one for a company that made software for small computers. The term personal computer would become commonplace later.
The company’s first product was a much-compressed version of the Basic programming language, designed to suit those underpowered machines. Yet the company’s big move came when it promised the computer giant IBM that it would deliver the operating system software for IBM’s entry into the personal computer business. Mr. Gates and Mr. Allen committed to supplying that software in 1980.
At the time, it was a promise without a product. But Mr. Allen was instrumental in putting together a deal to buy an early operating system from a programmer in Seattle. He and Mr. Gates tweaked and massaged the code, and it became the operating system that guided the IBM personal computer, introduced in 1981.
That product, called Microsoft Disk Operating System, or MS-DOS, was a watershed for the company. Later would come Microsoft’s immensely popular Windows operating system, designed to be used with a computer mouse and onscreen icons — point-and-click computing rather than typed commands. The company would also produce the Office productivity programs for word processing, spreadsheets and presentations.
“In his own quiet and persistent way, he created magical products, experiences and institutions, and in doing so, he changed the world,” Satya Nadella, Microsoft’s current chief executive, said of Mr. Allen in a statement.
Mr. Allen’s partnership with Mr. Gates began when they were teenagers attending the private Lakeside School in Seattle. It was there that they got their start in computing, working from a school Teletype terminal that was linked to a far-away mainframe computer under a so-called time-sharing computer system, in which operators paid for the computing time they used. Funds for the system were originally supplied by proceeds from a school bake sale.
Mr. Allen scored a perfect 1,600 on his SAT test, and went on to Washington State University. But after two years he dropped out to work as a programmer for Honeywell in Boston. Mr. Gates was nearby, attending Harvard University.
When an early microcomputer was introduced, appearing on the cover of Popular Electronics magazine, Mr. Allen persuaded Mr. Gates to drop out of Harvard and move to Albuquerque, where a start-up called MITS had built a machine that has been credited as the first personal computer. The machine lacked software, and Mr. Allen and Mr. Gates, showing up at the MITS offices, promised that they could supply it.
Their first offering was Microsoft Basic. Both Mr. Gates and Mr. Allen were skilled code creators, but Mr. Gates was more the hard-charging, volatile businessman, while Mr. Allen played the peacemaker and negotiator in those early days.
Within a few years, Microsoft moved from New Mexico to suburban Seattle. Though Mr. Allen stepped away from daily duties at Microsoft in the early 1980s, partly because of a deteriorating relationship with Mr. Gates, he remained on the Microsoft board until 2000.
“They were bemoaning my recent lack of production and discussing how they might dilute my Microsoft equity by issuing options to themselves and other shareholders,” Mr. Allen wrote.
But Mr. Allen held his ground and his shares.
Mr. Gates said in a statement on Monday: “From our early days together at Lakeside School, through our partnership in the creation of Microsoft, to some of our joint philanthropic projects over the years, Paul was a true partner and dear friend. Personal computing would not have existed without him.”
As Microsoft became the dominant personal computer software company, Mr. Allen, as well as Mr. Gates, who was the face of the company, became immensely wealthy. According to the Bloomberg Billionaires Index, he had a net worth of $26.1 billion.
He was also an investor and a generous philanthropist.
Mr. Allen donated more than $2 billion toward nonprofit groups dedicated to the advancement of science, technology, education, the environment and the arts. Among the scientific research organizations he funded were the Allen Institute for Brain Science in 2003 and the Allen Institute for Artificial Intelligence in 2014.
And while some of his philanthropy was global, like a passion for ending elephant poaching, much of his post-Microsoft work centered on Seattle, where he became a transformative force behind many of the city’s leading cultural institutions.
He restored the old Cinerama movie theater to modern standards seemingly ideal for watching science-fiction films, and he hired Frank Gehry to design the Museum of Pop Culture, which Mr. Allen founded in 2000 under the original name of the Experience Music Project. The wild, undulating building displayed items revealing Mr. Allen’s cultural obsessions, including guitars owned by Jimi Hendrix and Captain Kirk’s command chair from the 1960s television series “Star Trek.”
In the 1990s, Mr. Allen bought a swatch of land in the South Lake Union neighborhood to help build a Seattle version of Central Park, but the public ultimately voted down the plans. He took those real estate holdings and, through his company, Vulcan, developed South Lake Union into the home of Amazon. Google and other tech companies have been opening offices in that now revitalized neighbourhood.
“He has a definitive role of what we understand as today’s Seattle, which is about technology, about real estate and about a distinctive local culture with international visibility,” said Margaret O’Mara, a history professor at the University of Washington.
Mr. Allen also used his wealth to acquire the Portland Trail Blazers of the National Basketball Association in 1988 and the Seattle Seahawks of the National Football League in 1996.
Of all his investments, the ownership of professional sports teams was among the most incongruous. Sports owners, like it or not, are often in the spotlight, and Mr. Allen, by and large, had preferred to steer clear of media attention.
Yet in 1988, at 35, he bought the Trail Blazers and promised to keep the franchise in the city, one of the smallest in the league. He often flew to games from Seattle and sat courtside with his mother. Soon after he bought the team, the Trail Blazers had one of their best runs in franchise history, making it to the N.B.A. finals twice in three years, losing both times.
In a statement, Adam Silver, the N.B.A. commissioner, called Mr. Allen “the ultimate trail blazer — in business, philanthropy and in sports.” Mr. Silver said Mr. Allen, one of the longest-tenured owners in the league, was particularly interested in the league’s growth internationally and its embrace of new technologies.
In the mid-1990s, the owner of Mr. Allen’s hometown Seahawks, Ken Behring, was considering moving the team to Los Angeles because he was unable to get public funding for a new stadium in Seattle. Mr. Allen was urged to step in to keep the team in Seattle. In 1996, he bought an exclusive option to purchase the team from Mr. Behring by July 1997, an option he ultimately exercised, buying the team for $194 million.
Mr. Allen set about building the team a new home downtown. The team moved into CenturyLink Field in 2002, and Mr. Allen spent hundreds of millions of dollars to upgrade the stadium. Though he spoke infrequently to the media, he could often be seen at games, sometimes raising the “12” flag — representing the fans — before kickoff, a team ritual.
During his tenure the Seahawks made their only three Super Bowl appearances, winning the title once, in 2014.
“I personally valued Paul’s advice on subjects ranging from collective bargaining to bringing technology to our game,” Roger Goodell, the N.F.L. Commissioner, said in a statement.
One of Allen’s companies also owned a stake in the Seattle Sounders, one of the most successful franchises in Major League Soccer. The Sounders won the league title in 2016.
It is unclear what will happen to Mr. Allen’s teams; the details of his estate are not public. The Seahawks alone are worth an estimated $2.58 billion. Few N.F.L. and N.B.A. clubs change hands, so any sale is likely to attract substantial bids.
Paul Gardner Allen was born in Seattle on Jan. 21, 1953, to Kenneth and Edna (Faye) Allen. His father was a librarian; his mother a schoolteacher. He is survived by his sister, Jody Allen.
Three years ago, when commemorating Microsoft’s 40th anniversary, Mr. Allen posted on Twitter a bit of the code for the company’s first software product. At the top, it said, “Copyright 1975 by Bill Gates and Paul Allen.”
“It’s weird to look at bits of code you wrote 40 years ago and think, ‘That led to where Microsoft is today,’ ” Mr. Allen said at the time. He sounded genuinely amazed.