TGS
TGS is a three-letter acronym which may refer to:

Educational establishments
Tadcaster Grammar School, North Yorkshire, England
Takapuna Grammar School, Auckland, New Zealand
The Geneva School, Winter Park, Florida
Thetford Grammar School, Norfolk, England
Think Global School, New York City, United States
The Graduate School at Northwestern University. Illinois
Tiffin Girls' School, Kingston upon Thames, England
Tonbridge Grammar School, Tonbridge, England
Toowoomba Grammar School, Toowoomba, Australia
Tottenham Grammar School, London, England
Townsville Grammar School, Townsville, Australia
Trinity Grammar School, Melbourne, Australia
Trinity Grammar School, Sydney, Australia

Companies
TGS Management, American quantitative hedge fund
Transportadora de Gas del Sur, a Southern Natural Gas Transportation Company in Argentina
TGS-NOPEC Geophysical Company, a Norwegian geoscience data, software and service provider

Computing
The Great Giana Sisters

Media
Teen Girl Squad, a subcartoon from the Homestar Runner website cartoons
Tokyo Game Show, a video game trade show held in Tokyo
Taipei Game Show, a video game trade show held in Taipei
Toulouse Game Show, a video game trade show held in Toulouse, France
The Gathering Storm (novel), by Robert Jordan, of the Wheel of Time series
The Gamer Studio, a video gaming website.
The Girlie Show (fictional show), a fictional show in the television series 30 Rock
The Greatest Showman, a 2017 musical film
The Glass Scientists, an independent webcomic

Music
Tokyo Girls' Style, a Japanese girl group

Science
Triglycine sulfate, a material used in infrared sensors
Transcriptional gene silencing, a type of gene expression regulator