AtG or Alexander the Great

ATG in Military, short for Anti-Tank Gun

ATG, in genetics, the triplet code for the amino acid methionine

Art Technology Group, an ecommerce software developer

Art Theatre Guild, a Japanese film production company

ATG in bonding (glue, tape etc), is Adhesive Tape Gun

Alternative Tourism Group, a Palestinian NGO

Apple Computer's Advanced Technology Group

Anti-thymocyte globulin, antibodies to prevent and treat transplant rejection

Antigua and Barbuda, ISO 3-letter country code

The IATA code for the Tnte. Gral. Gerardo Pérez Pinedo Airport in Atalaya, Ucayali, Peru