TTO may refer to:

• Time-trade-off
• Tactical Technology Office, a division of DARPA
• Technology Transfer Office
• Transtrachreal oxygen, as used during Jet ventilation
• Trinidad and Tobago
• Toontown Online, a now-defunct 2003 Disney video game
• Trailing throttle oversteer, also known as lift-off oversteer
• Twist-to-open razor, a type of safety razor (see mention under Gillette (brand))
• Triple tibial osteotomy
• To-Take-Out - Medicine to take home after being hospitalised

• John of Gallura
• John of Gamala
• John of Garland
• John of Garlande
• John of gaunt
• John of Genoa
• John of Gibelet
• John of Giscala
• John of Gischala
• John of Gloucester
• John of Gmund
• John of Gmunden
• John of God (Medium)
• John of God (medium)
• John of God, Saint
• John of Gorze
• John of Gravina
• John of Greenford
• John of Guildford
• John of Hauteville
• John of Hauville
• John of Hazelgreen
• John of Hildesheim
• John of Hollywood
• John of Ireland