Gates has come to be known for his aggressive business tactics and confrontational style of management.
He, and his company, have attracted a vast army of critics and enemies in recent years as their domination of the IT world has grown.
He was born on 28 October, 1955, growing up with two sisters in Seattle. Their father, William H. Gates II, is a Seattle attorney, and their late mother, Mary Gates, was a schoolteacher.
Gates began computing as a 13-year-old at the city's Lakeside school.
By the age of 17, he had sold his first program - a timetabling system for the school, earning him $4,200.
It was at Lakeside that he met fellow student Paul Allen, who shared his fascination with computers.
During Gates' stint at Harvard, the two teamed up to write the first computer language program written for a personal computer.
The PC's maker, MITS, liked their work and the two friends established Microsoft in 1975, so-called because it provided microcomputer software.