William Napier
William Napier may refer to:
- William Ewart Napier, American chess master
- William Francis Patrick Napier, British soldier and military historian
- William Napier (astronomer), astronomer and author
- William Napier, 9th Lord Napier, Royal Navy officer, politician and diplomat
- William Napier (novelist), historical novelist pseudonym of Christopher Hart
- William Napier (VC), English recipient of the Victoria Cross
- William Napier (Royal Navy officer), British admiral
- William Craig Emilius Napier, British general
- William Napier (lawyer), Singapore lawyer and newspaper editor; Lieutenant-Governor of Labuan
- William Joseph Napier, member of parliament for Auckland, New Zealand
- William Napier, 11th Lord Napier, British peer
- William Napier, 13th Lord Napier, Scottish soldier and courtier
- William Napier, 7th Lord Napier, Scottish peer
- Sir William Napier, 3rd Baronet, British baronet and soldier