Bill Gates's legal name is William Henry Gates III

The name ‘Bill Gates’ is a widely recognized global moniker, but his official legal name is William Henry Gates III. The name ‘Bill’ is a traditional English diminutive of ‘William’ that dates back to the Middle Ages.

He is the third generation of his family to bear the name. His grandfather was William Henry Gates Sr., a veteran and former bank director in Washington, and his father was William Henry Gates Jr., a lawyer and co-founder of the Bill & Melinda Gates Foundation. To avoid confusion within the family due to the shared name, he was also known by the childhood nickname ‘Trey’.