| I |
| I FFORCEV | I Field Force, Vietnam |
| I&E | Information and Education |
| I&M | Improvement and Modernization |
| I&PR | Information and Public Relations Bloc |
| I/W | Individual Weapon |
| IAACONS | Improved ARVN Ammunition Control System |
| IAAD | Information Advisory and Accreditation Division |
| IAD | Information Advisory Division |
| IAS | Indicated Air Speed |
| IBM | International Business Machine |
| IC EX | Infrastructure Intelligence Coordination and Explanation |
| ICC | International Control Commission |
| ICC | Inventory Control Center |
| ICCS | International Commission of Control and Supervision |
| ICCV | Inventory Control Center, RVN |
| ICEX | Infrastructure Intelligence Coordination and Exploitation |
| ICM | Improved Conventional Munitions |
| ICN | Idle Channel Noise |
| ICP | In-Country Procurement |
| ICP | Indochinese Communist Party Formed in January, 1930 by Ho Chi Minh, it was dissolved on November 11, 1945 and replaced by the Lien Viet.
|
| ICP | Intelligence Collection Plan |
| ICP | Inventory Control Point |
| ICR | Intelligence Collection Requirement |
| ICRC | International Committee of the Red Cross |
| ICS | Integrated Communications System |
| ICS | Intercommunication system |
| ICS-SEA | Integrated Communications System - Southeast Asia |
| ICSC | The International Control and Surveillance Commission. See ICC |
| ICTZ | First Corps Tactical Zone |
| ID | Identification; to make identification |
| ID | Intelligence Division |
| IDC | Industrial Development Center |
| IDCSS | Initial Defense Communications Satellite System |
| IDHS | Intelligence Data Handling System |
| IESS | Inter-service Excess Screening System |
| IFF | Identification, Friend or Foe; aircraft transponding beacon received by radar distinguishing friend from foe. |
| IFFORCEV | I Field Force, Vietnam |
| IFR | Instrument Flight Rules |
| IFR | Intermediate Frequency Radar |
| IFS | Inshore Fire Support Ship |
| IG | Inspector General |
| II FFORCEV | II Field Force, Vietnam |
| IID | Infrared Intrusion Detectors |
| IIFFORCEV | II Field Force, Vietnam |
| IIMS | Intensive Items Management System |
| ILA | International Longshoremens Association |
| ILC | International Logistics Center |
| ILS | Instrument Landing System |
| IMAO | International Military Assistance Office |
| Immelmann | Maneuver in which the air-craft completes the first half of a loop and then rolls over to an upright position thus changing direction 180 degrees with a simultaneous gain in altitude. |
| IMN | Indicated Mach Number |
| IND | Indicators |
| Ind Wpn(s) | Individual Weapon(s) |
| Inf/INF | Infantry |
| Institutions | Organized way of solving societies' problems, each institution possessing an underlying concept set for societal survival. |
| Instl | Installation |
| INTBUL | Intelligence Bulletin |
| INTC | Intelligence Corps |
| Intel | Intelligence |
| Internal Security | The state of law and order within a nation as determined by the government's capability to cope with violence, subversion and lawlessness and the prevailing public confidence in that capability. |
| INTSUM | Intelligence Summary |
| IO | Information Office/Officer |
| IOC | Initial Occupational Capability |
| IP | Initial Point; a well-defined point, easily distinguishable visually and/or by radar, used as a starting point for a bomb run to the target. |
| IP | Inside Plant |
| IPC | Irregular Practices Committee |
| IR | Infrared |
| IR missile | An infrared or heat-seeking missile |
| IR-GFD | Infrared Gun Flash Detector |
| IRAN | Inspection and Repair as Necessary |
| IRF | Immediate Reaction Force |
| IRGFD | Infrared Gun Flash Detector |
| IRHA | Injuries Resulting from Hostile Action |
| IRON HAND | A code name for a flight with special ordnance and avionics equipment whose mission is to seek and destroy enemy surface-to-air missile sites. |
| Irregular Forces | Armed individuals or groups who are not members of the regular armed forces, police or other internal security forces. |
| IRS | Internal Revenue Service |
| IRWG | Information and Reports Working Group (MACV) |
| ISA | Internal Security Affairs |
| ISA | International Security Affairs |
| ISA | International Security Agency |
| ISB | Intermediate Support Base |
| ISC | Infiltration Surveillance Center |
| ISD | Instructional System Development |
| ISSA | Interservice Support Agreement |
| IST | Instructor In-Service Training |
| ITACS | Integrated Tactical Air Control System |
| ITO | Installation Transportation Office |
| IVS | International Voluntary Services |
| IW | Individual Weapon |
| IWCS | Integrated Wideband Communications System |