St Louis Grammar School is a school in Ballymena, Northern Ireland.
| Motto | Ut Sint Unum ('That we all may be one') |
|---|---|
| Established | 1924 |
| Type | Grammar foundation school |
| Headteacher | Mr Sean Rafferty |
| Location | Ballymena Antrim Northern Ireland |
| Students | 981 |
| Gender | Unisex |
| Ages | 11–19 |
| Website | SLGS |
The school has participated in all Ireland finals of Camogie. The school came 5th overall in all of the United Kingdom in the Times Spelling Bee.
The Choir in 2009 came first in the Ballymena district and have a very renowned chamber choir singing with Peter Corey in December 2010 at the Music Box.