HART
- Halt All Racist Tours
- Hart (disambiguation)
- Hazardous area response team
- Health Advisory and Recovery Team
- Heterogeneous Aerial Reconnaissance Team
- Highly active antiretroviral therapy
- Highway Addressable Remote Transducer Protocol
- Hillsboro Artists' Regional Theatre
- Hillsborough Area Regional Transit
- Housatonic Area Regional Transit
- Human Assisted Reproductive Technology
- Huntington Area Rapid Transit
- Hypervelocity Aircraft Rocket, Tactical
- Rapid response team (medicine)
- Skyline (Honolulu)