William or Bill Warner may refer to:

• William Warner (poet) (c. 1558–1609), English poet
• William H. Warner (1812–1849), officer in the U.S. Army's Corps of Topographical Engineers
• William Smith Warner (1817–1897), American politician
• William Warner (Missouri politician) (1840–1916), American politician
• William Warner (cricketer) (1844–1871), English cricketer
• William John Warner or Cheiro (1866–1936), Irish astrologer and palmist
• William Warner (Conservative politician) (1867–1950), British Army officer and politician
• Bill Warner (American football) (1881–1944), American football player and coach
• W. Lloyd Warner (1898–1970), American anthropologist
• William W. Warner (1920–2008), American author, winner of a Pulitzer Prize in 1977
• Bill Warner (motorcyclist) (1969–2013), American motorcycle racer
• William Warner (Michigan politician, born 1806) (1806–?), American politician
• William Warner (Michigan politician, born 1812) (1812–1868), American politician

• Bill Warner (disambiguation)
• Warner (surname)