Tom Johnston, Thomas Johnston or Tommy Johnston may refer to:
Thomas A. Johnston (1848–1934), US educator
Thomas Alan Johnston (born XXth c.), Scottish engineer
Thomas Dillard Johnston (1840–1902), US political figure
Thomas E. Johnston (born 1967), US federal judge
Thomas George Johnston (1849–1905), Canadian physician and political figure
Thomas Henry Johnston (1880–?), New Zealand tram conductor, labourer, miner and strike-breaker
Thomas Johnston (Canadian politician) (1821–1903), Canadian industrial and political figure
Thomas L. Johnston (1927–2009), Scottish scientist
Tom Johnston (footballer) (1918–1994), Scottish midfielder; playing career 1938–1956; coaching and managerial career 1956–1978
Tom Johnston (DJ), (born 1993), Australian DJ and musician; pioneer of the Tropical House subgenre
Tom Johnston (musician) (born 1948), US musician, co-founder of The Doobie Brothers
Tom Johnston (Saskatchewan politician) (1881–1969), British-born Canadian political figure
Tom Johnston (Scottish politician) (1881–1965), Scottish political figure
Tommy Johnston (1927–2008), Scottish athlete in football