Class 37 may refer to:
- British Rail Class 37, a British diesel locomotive
- BHP Newcastle 37 class, a class of Australian diesel locomotives
- LT&SR 37 Class, a class of British tank locomotives
- DRG Class 37, a class of German steam locomotives with 2-6-0 wheel arrangements operated by the Deutsche Reichsbahn:
- Class 37.0-1: Prussian P 6
- Class 37.1-2: PKP Class Oi1
- Class 37.2: LBE G 6
- Class 37.3: ČSD Class 344.0
- Class 37.4: PKP Class Oi101