William Mallinson may refer to:

• William Mallinson (auctioneer), involved with the Sugarman Gang
• Sir William Mallinson, 1st Baronet (1854–1936) of the Mallinson Baronets
• Sir William James Mallinson, 2nd Baronet (1879–1944) of the Mallinson Baronets
• Sir (William) Paul Mallinson, 3rd Baronet (1909–1989) of the Mallinson Baronets
• Sir William John Mallinson, 4th Baronet (1942–1995) of the Mallinson Baronets
• Sir (William) James Mallinson, 5th Baronet (b. 1970) of the Mallinson Baronets

• Iton (butterfly)
• Itonididae
• It Only Hurts when I'm Breathing
• I, Too, Am Harvard
• I, Too, Have Seen the Woods
• I took an arrow in the knee
• Itoo Risa
• IT operations analytics
• I Torneo Challenger ATP Marbella Open
• Itoro Coleman
• Ito Sekisui V
• Itoshiki Hibi yo
• Itoshi kimi e
• Itoshi Kimi e
• Itoshima
• Ito Sukeyuki
• Ito Teiji
• I Touch Roses
• I Touch Roses (Book of Love song)
• I Touch Roses: The Best of Book of Love
• Itou Ittousai
• Itou Kanae
• Itou Makoto
• Itou Masumi
• Itou Mima