William Thayer
William Thayer may refer to:
- William Greenough Thayer, American educator
- W. Paul Thayer, American test pilot, aviation executive, and Deputy Secretary of Defense during the Reagan Administration
- William Roscoe Thayer, American author and editor
- William Sydney Thayer , American Consul General to Egypt - see United States Ambassador to Egypt
- William Sydney Thayer, American physician and professor of medicine
- W. W. Thayer, American politician, governor of Oregon, and Oregon Supreme Court chief justice
- William Wilde Thayer, one of the founders of the short-lived Thayer & Eldridge publishing firm
- William Thayer Arteaga, Chilean politician