William Arnott may refer to:
- William Arnott (biscuit manufacturer) (1827–1901), Australian manufacturer and businessman
- William Arnott (politician) (1832–1907), American farmer and politician
- Bob Arnott or William Robert Arnott (1922–2016), Australian skier
- W. Geoffrey Arnott (1930–2010), British Hellenist
- Sir William Melville Arnott (1909–1999), Scottish academic