William Henry Gates III (born October 28, 1955) is an American business magnate, software developer, investor, author, and philanthropist. He is the co-founder of Microsoft Corporation. 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.

Gates was born and raised in Seattle, Washington. In 1975, he co-founded Microsoft with childhood friend Paul Allen in Albuquerque, New Mexico. It became the world's largest personal computer software company. Gates led the company as chairman and CEO until stepping down as CEO in January 2000, succeeded by Steve Ballmer, but he remained chairman of the board of directors and became chief software architect. During the late 1990s, he had been criticized for his business tactics, which have been considered anti-competitive. This opinion has been upheld by numerous court rulings. 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 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 1987, he has been included in the Forbes list of the world's wealthiest people. From 1995 to 2017, he held the Forbes title of the richest person in the world every year except from 2010 to 2013. In October 2017, he was surpassed by Amazon founder and CEO Jeff Bezos, who had an estimated net worth of US$90.6 billion compared to Gates's net worth of US$89.9 billion at the time. As of April 2021, Gates had an estimated net worth of US$146.7 billion, making him the third-richest person in the world.

Later in his career and 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.
