William Henry Gates III (born October 28, 1955) is an American business magnate, software developer, investor, author, and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions of chairman, chief executive officer (CEO), president, and chief software architect, while also being the largest individual shareholder until May 2014. He is considered one of the best-known entrepreneurs of the microcomputer revolution of the 1970s and 1980s.

In June 2008, Gates transitioned to a part-time role at Microsoft and full-time work at the Bill & Melinda Gates Foundation, the private charitable foundation he and his then-wife, Melinda Gates, established in 2000. He stepped down as chairman of the board of Microsoft in February 2014 and assumed a new post as technology adviser to support the newly appointed CEO Satya Nadella. In March 2020, Gates left his board positions at Microsoft and Berkshire Hathaway to focus on his philanthropic efforts including climate change, global health and development, and education.

since leaving day-to-day operations at Microsoft in 2008, Gates has pursued many business and philanthropic endeavors. He is the founder and chairman of several companies, including BEN, Cascade Investment, bgC3, and TerraPower. He has given sizable amounts of money to various charitable organizations and scientific research programs through the Bill & Melinda Gates Foundation, reported to be the world's largest private charity. Through the foundation, he led an early 21st-century vaccination campaign which significantly contributed to the eradication of the wild poliovirus in Africa. In 2010, Gates and Warren Buffett founded The Giving Pledge, whereby they and other billionaires pledge to give at least half of their wealth to philanthropy.