Class 6
- BR Standard Class 6
- China Railways JF6
- Class 06 (disambiguation)
- Class VI (U.S. Army)
- HAZMAT Class 6 Toxic and infectious substances
- I-6-class submarine
- Indian locomotive class WAG-6A
- Indian locomotive class WAP-6
- Indian locomotive class WCM-6
- Indian locomotive class WDG-6G
- Indian locomotive class WDM-6
- Indian locomotive class WDS-6
- LNER Class O6
- LSWR G6 class
- LSWR T6 class
- LSWR X6 class
- MGWR Class 6
- Midland Railway 6 Class
- Milwaukee Road class F6
- NSB Di 6
- NSB El 6
- Norway
- P 6-class torpedo boat
- Pennsylvania Railroad E6 class
- Pennsylvania Railroad class B6
- Pennsylvania Railroad class H6
- Red Flag 6-class locomotive
- SCORE Class 6
- SR Class 6Pul
- Sa'ar 6-class corvette
- Secure Digital
- South African Class 6 4-6-0
- South African Class 6E 4-6-0
- Southern Pacific class AC-6
- Southern Pacific class GS-6
- Southern Pacific class MC-6
- TS Class 6
- Truck classification
- Type 6 (disambiguation)
- VR Class Sm6