ATO may refer to:
- Abort to Orbit, an intact abort procedure for Space Shuttle launches
- Accumulated Time Off, a method of accumulating paid or unpaid absence hours based on hours worked
- African Timber Organization, for sustainable forest management
- Air Tasking Order, (United States Air Force)
- Air Traffic Organization, an FAA terminology
- Air Training Officer, a former position at the United States Air Force Academy
- Air Transportation Office (Philippines), agency of the Philippine government
- Alpha Tau Omega, an American student fraternity
- Alpha Tau Omega (Philippines), a Filipino student fraternity
- Alpha Team Omega (United States) Subsidiary of Watching.I.Inc
- Alternative Trading Organization, an NGO focusing on Fair Trade exports
- Amiga Translators' Organization, an organization for translating Commodore Amiga applications
- Ammunition Technical Officer, a designation in the British Armed Forces
- Anti-Terrorism Officer, a position in the Homeland Security Community
- Arab Towns Organization, a network to promote cooperation between and development of Arab cities
- Assemble To Order, see configure-to-order
- Assisted take off
- ATO, the Amtrak station code for Atco (NJT station), New Jersey, U.S.A.
- ATO Records, a record label
- Atmos Energy Corporation's ticker symbol on the New York Stock Exchange
- Australian Taxation Office, the Australian government tax agency
- Authority to Operate, U.S. Government's final approval for a system or program to operate in a given environment
- Automatic train operation
- Amateur Try-Out, a type of ice hockey contract
- Chemotherapy, Arsenic trioxide a potent chemotherapeutic agent for acute promyelocytyc leukemia
- ATO fuse
Ato may refer to:
- A cacodemon of the Enochian angels
- Ato, Yamaguchi – a Japanese town
- Osman Ali Atto also written Osman Ali Ato, a Somali warlord
- One of three 2002 Football World Cup mascots