William Thayer

William Thayer may refer to:


 * William Greenough Thayer (1863–1934), American educator


 * W. Paul Thayer (1919–2010), American test pilot, aviation executive, and Deputy Secretary of Defense during the Reagan Administration
 * William Roscoe Thayer (1859–1923), American author and editor
 * William Sydney Thayer (consul) (died 1864), American Consul General to Egypt (1861–1864) - see United States Ambassador to Egypt
 * William Sydney Thayer (1864–1932), American physician and professor of medicine
 * W. W. Thayer (William Wallace Thayer, 1827–1899), 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 (c. 1860–1861)
 * William Thayer Arteaga (1918–2018), Chilean politician