William Mair may refer to:

• William Mair (South Australian politician) (died 1897), member of the South Australian House of Assembly
• Bill Mair (1900–1964), Australian politician, member of the Victorian Legislative Council
• William Mair (chemist) (1868–1948), Scottish pharmacist and manufacturing chemist
• William Mair (moderator) (1830–1920), Scottish minister
• William Crosbie Mair (died 1831), Scottish physician
• William Gilbert Mair (1832–1912), soldier, resident magistrate, and judge in New Zealand

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