Just over 20 years after stepping down as CEO of Microsoft and six years after relinquishing his position as Chairman of the Board, Microsoft cofounder Bill Gates has resigned from the Microsoft Board of Directors. Gates, 64, is leaving the board to spend more time on philanthropic ventures.

"I have made the decision to step down from both of the public boards on which I serve—Microsoft and Berkshire Hathaway—to dedicate more time to philanthropic priorities including global health and development, education, and my increasing engagement in tackling climate change," Gates wrote in a post on LinkedIn announcing the decision. "The leadership at the Berkshire companies and Microsoft has never been stronger, so the time is right to take this step."

Gates founded Microsoft in 1975 with Paul Allen, and their first product was Altair BASIC. The company's breakout product was Windows, which became the world's most-used desktop operating system. Gates steered the company through a period of massive growth but also set the table for his successor, Steve Ballmer, to deal with antitrust issues. Microsoft was found by both US and European regulators to have abused its dominant market position for both Web browsers and operating systems in the 2000s, which resulted in fines and consent decrees.

In 2000, Gates used $5 billion of his personal fortune to launch the Bill and Melinda Gates Foundation, which has become one of the largest philanthropic ventures in the world.

“On behalf of our shareholders and the Board, I want to express my deep appreciation to Bill for all his contributions to Microsoft. As a member of the Board, he challenged us to think big and then think even bigger. He leaves an enduring legacy of curiosity and insight that serves as an inspiration for us all,” said John W. Thompson, Microsoft independent board chair.