William Sinclair

William Sinclair may refer to:

Nobility

 * William Sinclair, 1st Earl of Caithness (1410–1484), Scottish nobleman
 * William Sinclair, 2nd Earl of Caithness (1459–1513), Scottish nobleman
 * William Sinclair, 10th Earl of Caithness (1727–1779), Scottish nobleman

Politicians

 * William Pirrie Sinclair (1837–1900), MP for Antrim and Falkirk Burghs
 * W. E. N. Sinclair (1873–1947), Canadian barrister, solicitor and politician
 * William Henry Sinclair (1864–1902), Canadian politician in the Legislative Assembly of the Northwest Territories

Religious figures

 * William Sinclair (bishop) (died 1337), bishop of Dunkeld
 * William Sinclair (priest) (1804–1878), Scottish author and rector of Pulborough, Sussex
 * William Sinclair (archdeacon of London) (1850–1917), Anglican priest and author
 * William Sinclair (United Irishmen) (died 1830), Irish revolutionary

Others

 * William Sinclair (cricketer) (1846–1869), Australian cricketer
 * William Sinclair (footballer) (born 1934), Scottish footballer
 * William Sinclair (fur trader) (1790s–1868), chief factor of the Hudson's Bay Company
 * William H. Sinclair (1838-1897) Businessman; Union Officer
 * William John Sinclair (1877–1935), American geologist and paleontologist
 * William Angus Sinclair (1905–1954), Scottish philosopher
 * Will Sinclair, a character in Angel in My Pocket