William Denny may refer to:

• William Denny (MP) (1578–1625), English lawyer and politician
• William Denny, deputy governor of the Province of Pennsylvania, 1756-1759
• William Denny Jr. (born 1930), American politician in the Mississippi House of Representatives
• William Denny and Brothers, British shipbuilder based in Dumbarton, Scotland
• William Alexander Denny or Bill Denny (medical researcher) (born 1943), New Zealand chemist
• William F. Denny (c. 1860–1908), American vaudeville performer and pioneer recording artist
• William H. P. Denny (1811–1890), American newspaper editor and publisher and politician in Ohio
• William Joseph Denny or Bill Denny (1872–1946), South Australian politician