Microsoft co-founder Paul Allen died of cancer Monday afternoon, Xinhua news agency quoted his family as saying.
The founder of Vulcan Inc was 65.
The company said in a statement that Allen died from complications of non-Hodgkin's lymphoma in Seattle, hailing him as a "noted technologist, philanthropist, community builder, conservationist, musician and supporter of the arts."
His sister, Jody, described the Microsoft co-founder as "a remarkable individual on every level."
"While most knew Paul Allen as a technologist and philanthropist, for us he was a much-loved brother and uncle, and an exceptional friend," she said.
Sitting Microsoft CEO Satya Nadella said Allen had made "indispensable" contributions to Microsoft and the technology industry.
In 1975, Allen created Microsoft with childhood friend Bill Gates. Gates, who is also co-chair of the Bill and Melinda Gates Foundation, mourned Allen's death, saying that he was "heartbroken by the passing of one of my oldest and dearest friends, Paul Allen."
"From our early days together at Lakeside School (in Seattle), 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," Gates said in a statement.
Allen founded Vulcan in the mid-80s to invest in several media and communications companies. He also worked on philanthropic projects and invested in professional sports teams. He had owned the United States (US) National Football League's Seahawks since 1997 and also owned the NBA's Portland Trail Blazers.
Allen was one of the world's richest people and ranked 44th on Forbes' 2018 list of billionaires with an estimated net worth of more than US$20 billion as of Monday.