Thomas Barnett may refer to:

• Thomas Barnett (musician) (born 1973), American singer and songwriter
• Thomas P. Barnett (1870–1929), American architect and painter
• Thomas P. M. Barnett (born 1962), American military geostrategist
• Thomas Speakman Barnett (1909–2003), Canadian politician
• Thomas Barnett (Niagara Falls) (1799–1890), museum proprietor, collector and innkeeper
• Thomas Barnett (footballer) (1876–?), English footballer
• Tom Barnett (American football) (born 1937), former professional American football player
• Tom Barnett (footballer) (1936–2022), English footballer
• Tommy Barnett (footballer) (1908–1986), English footballer
• Tommy Barnett (pastor), American author and pastor