| H |
| H | Time Zone for Saigon (i.e., 2000H) |
| H&I | Harassing and Interdiction Fires |
| HA | Helicopter Ambulance |
| HAC | Headquarters Area Command |
| HAL | Helicopter Attack Squadron |
| HALO | High Altitude Low Opening |
| HANDSID | Hand Emplaced Seismic Intrusion Detector |
| Hard turn | A planned turn in which the intensity of the turn is governed by the angle-off and range of the attacking aircraft. |
| HAWS | Heavy Artillery Warning System |
| HAZCON | Hazardous Condition |
| HCU | Harbor Clearance Unit |
| HDU | Harbor Defense Unit |
| HE | High Explosives |
| HEAT | Armament switch setting for using infrared missiles. |
| HEAT | High Explosive, Antitank |
| HECP | Harbor Entrance Control Post |
| Hectare | Vietnamese Government official unit of land measure. 2.471 acres, or 10,000 square meters. |
| HEDSUPPACT | Headquarters, Support Activity, Saigon (HSAS) |
| Hel | Helicopter |
| HELO | Helicopter |
| HELOSID | Helicopter Deliverable Seismic Intrusion Detectors |
| HEP | High Explosive Plastic |
| HES | Hamlet Evaluation System |
| HEW | Hamlet Evaluation Worksheet |
| HF | High Frequency |
| HF SSB | High Frequency, Single Side Band |
| HG | Headquarters |
| HHG | Household Goods |
| HIMS | Historical Information Management System |
| HIS | Heliborne Illumination System |
| HJMA | Highland Junior Military Academy |
| HKG | Government of Hong Kong |
| HLS | Helicopter Landing Site(s) |
| HLZ | Helicopter Landing Zone |
| HMAS | Her Majesty's Australian Ship |
| HMG | Her Majesty's Government |
| HMM | Marine Helicopter Squadron Medium |
| HNC | High National Council |
| HO-51 | Computer System |
| Hoa Hao | Organized religious sect involved in the political movement (struggle) in South Vietnam, armed by French to resist Viet Minh. |
| Hoi Chanh | VC/NVA Rallier |
| Hop Tac | "Many Working Together" |
| Hot mike intercom | Intercommunication system continuously active (hot). |
| House 50 | Logistical Support Center located at Number 50 Plantation Road, Saigon. |
| How Bn | Howitzer Battalion |
| HP | Horse Power |
| HQ | Headquarters |
| HQ COMDT | Headquarters Commandant |
| HQS | Headquarters |
| Hr/HR | Hour |
| HSAS | Headquarters, Support Activity, Saigon, (HEDSUPPACT) |
| HSR | Human Sciences Research |
| HSSC | Heavy Salvage Craft |
| HTA | High Threat Area |
| HUGHES | Hughes Aircraft, Inc. |
| HUMINT | Human Intelligence |
| HvHel | Heavy Helicopter |
| HVRP | High Value Reward Program |