ATAC, or Atac, may refer to:

• Airborne Tactical Advantage Company, a U.S. government contractor which operates foreign military aircraft for training purposes
• Anti-Terrorist Action Command, a fictional police organization in the 1981 movie Nighthawks
• Navy Antiterrorist Alert Center, the 1983–2002 United States Navy terrorism watch center
• "Arimidex, Tamoxifen, Alone or in Combination", an international trial of treatments for localized breast cancer
• Asbestos Testing and Consultancy Association, a UK trade association
• Assay for Transposase-Accessible Chromatin (ATAC-seq), a DNA sequencing technique
• Atac, a French supermarket chain
• ATAC SpA (Azienda per i Trasporti Autoferrotranviari del Comune di Roma), a public transport company in Rome, Italy
• Automatic targeting attack communicator, a fictional military communication device in the James Bond movie For Your Eyes Only
• Advanced Technology Airborne Computer (ATAC) was a computer used on US naval aircraft and the NASA Galileo (spacecraft).

• Ataç, list of people with a similar Turkish name