EKU or Eku may stand for:
- Eastern Kentucky University, an American university
- Eku, a Japanese weapon
- EKU, a former German brewery and now brand of Kulmbacher Brewery
- Earliest known use, a philately term usually referring to the first day of issue of a postage stamp or postmark
- European Karate Union, now European Karate Federation (EKF)
- Extended Key Usage, a digital certificate