ATO may refer to:

• Abort to Orbit, an intact abort procedure for Space Shuttle launches
• Arsenic trioxide a potent chemotherapeutic agent for acute promyelocytic leukemia
• ATO fuse
• Automatic train operation
• Assisted take off

• Air Tasking Order, (United States Air Force)
• Air Training Officer, a former position at the United States Air Force Academy
• Ammunition Technical Officer, a designation in several armed forces
• Anti-Terrorist Operation in Ukraine, the Ukrainian government's operation in the war in Donbas, 2014-current time, since 2018 it has been called Joint Forces Operation.
  • ATO zone, the official name for territory where the war in Donbas takes place
• A US Navy hull classification symbol: Fleet tug, old (ATO)

• Alpha Tau Omega, an American student fraternity
• Alpha Tau Omega (Philippines), a Filipino student fraternity
• Alternative Trading Organization, an NGO focusing on Fair Trade exports
• Air Traffic Organization, a division of the Federal Aviation Administration
• Air Transportation Office (Philippines), agency of the Philippine government
• Arab Towns Organization, a network to promote cooperation between and development of Arab cities
• ATO Records, a record label
• Australian Taxation Office, the Australian government tax agency

• Ato, another name for dap-ay, traditional meeting places of various ethnic groups in the northern Philippines
• Account takeover, a form of payments and online fraud
• Assemble To Order, see build to order
• Asset turnover
• ATO, the Amtrak station code for Atco (NJT station), New Jersey, U.S.A.
• Atmos Energy Corporation's ticker symbol on the New York Stock Exchange
• Authority to Operate, part of a Risk Management Framework
• Amateur Try-Out, a type of ice hockey contract

• Ato, Yamaguchi – a Japanese town
• Ato Station

• Osman Ali Atto also written Osman Ali Ato, a Somali warlord
• One of three 2002 Football World Cup mascots
• All pages with titles beginning with ATO
• All pages with titles containing ATO