- The American Historical Association
- a-ha, a Norwegian pop music band
- American Heart Association
- American Hockey Association
- American Homebrewers Association
- American Humanist Association
- American Humane Association
- Alpha Hydroxy Acid
- aha! In some languages it's an exclamation used when one gets a sudden idea, or simply in a moment of discovery or clarity, often a moment of surprise.ja:AHA
