HTO may refer to:

• HTO Park a beach in Toronto, Ontario, Canada

• East Hampton Airport, in New York, United States
• Hightown railway station, in England

• High tibial osteotomy
• High Temperature Oxide
• Hohmann transfer orbit
• Holocene thermal optimum
• Waco HTO, an American biplane
• Partially tritiated water

• Hostile takeover
• Hellenic Tourist Organisation

• Haupttreuhandstelle Ost, a Nazi state institution in occupied Poland
• Minica Huitoto, spoken in Colombia and Peru
• OTE, a Greek telecommunications company