William Henry Gates III  is an American businessman and philanthropist.

He is pioneer of the microcomputer revolution of the 1970s and 1980s who became a billionaire in 1987—then the youngest ever, at age 31. Gates is founder and chairman of several other companies, including BEN, Cascade Investment, TerraPower, Gates Ventures, and Breakthrough Energy.

In 2010, he and Warren Buffett founded the Giving Pledge, whereby they and other billionaires pledge to give at least half their wealth to philanthropy. Named as one of the 100 most influential people of the 20th century by Time magazine in 1999, he has received numerous other honors and accolades, including a Presidential Medal of Freedom, awarded jointly to him and French Gates in 2016 for their philanthropic work. The subject of several documentary films, he published the first of three planned memoirs, Source Code: My Beginnings, in 2025.