Ati

As a word, Ati or ATI may refer to:
 * Ati people, a Negrito ethnic group in the Philippines
 * Ati language (Philippines), the language spoken by this people group
 * Ati-Atihan festival, an annual celebration held in the Philippines
 * Ati language (China), an unclassified Loloish language of Huaning County, Yunnan, China
 * Ati, a queen of the fabled Land of Punt in Africa
 * Ati, Chad, a town in Chad
 * Ati, Iran, a village in Khuzestan Province, Iran
 * Maha Ati, one of the nine subdivisions of Buddhist Tantra in the Nyingma school

The acronym ATI may refer to:

Academic institutions

 * Auckland Technical Institute, now the Auckland University of Technology, Auckland, New Zealand
 * Ohio State University Agricultural Technical Institute, known as Ohio State ATI
 * An associate of the Tax Institute of Australia

Electronics and information technology

 * ATI Technologies, a former Canadian semiconductor company manufacturing GPUs and chipsets
 * Acronis True Image, cloning and backup software
 * Allied Telesis, a telecommunications company, formerly Allied Telesyn
 * Tunisian Internet Agency, also known as ATI (short for Agence tunisienne d'Internet), telecommunications company in Tunisia

Companies

 * ATI Physical Therapy

Transportation

 * Aero Trasporti Italiani, a defunct Italian airline (ICAO designator)
 * Air Transport International, a charter cargo airline
 * Artigas Airport, IATA designation

Other uses

 * Above threshold ionization, a photoelectrochemical process ionizing an atom by an excessive number of photons
 * Allegheny Technologies Incorporated, a specialty metals company headquartered in Pittsburgh, Pennsylvania, USA
 * Access to Insight, a Theravada Buddhist website
 * Associated Television International, a production and distribution company
 * Astatine monoiodide, a radioactive molecule
 * Amylase/trypsin inhibitor, a substance that inhibits the enzymes amylase or trypsin (see Non-celiac gluten sensitivity)