Ian Stewart may refer to:

• Ian Stewart (RAF officer), current United Kingdom National Military Representative, Supreme Headquarters Allied Powers Europe
• Ian MacAlister Stewart (1895–1987), brigadier general during the Second World War
• Ian Michael Stewart, former senior commander in the Royal Air Force

• Ian Stewart (Labour politician) (born 1950), Scottish politician
• Ian Stewart, Baron Stewartby (1935–2018), British Conservative Party politician and former MP for Hitchin, England

• Ian Stewart (athlete) (born 1949), Scottish Olympic athlete
• Ian Stewart (Australian rules footballer) (born 1943), member of the Australian Football Hall of Fame
• Ian Stewart (baseball) (born 1985), major league baseball player
• Ian Stewart (Northern Ireland footballer) (born 1961), member of the 1986 Northern Ireland Football World Cup team
• Ian Stewart (racing driver) (1929–2017), Scottish Formula One driver
• Ian Stewart (Scottish footballer) (born 1945/46), Scottish football player and manager

• Ian Stewart (mathematician) (born 1945), English academic and science fiction author
• Ian Stewart (musician) (1938–1985), British musician and early member of the Rolling Stones
• Ian Stewart (police commissioner), former Commissioner of the Queensland Police Service (2012–2019)
• Ian Stewart, founder of Gremlin Interactive and Zoo Digital
• Ian Stewart (priest) (born 1943), Dean of Brechin
• Ian Charles Stewart (born 1958), entrepreneur and co-founder of Wired magazine
• Ian Duncan Stewart (1938–2017), or Ian Brady, British serial killer and author
• Ian Edward Stewart (1908–1989), English pianist and bandleader, Savoy Orpheans

• Iain Stewart (disambiguation)
• Ian Stuart (disambiguation)