William Sykes may refer to:
- Bill Sykes (born 1948), Member for Benalla in the Victorian Parliament
- William Sykes (convict) (1827–1891), convict transported to Western Australia
- William Sykes (clergyman) (1861–1930), Anglican clergyman
- William Sykes (businessman), English manufacturer of sporting goods
- William Henry Sykes (1790–1872), Indian Army officer