| Abbreviation | Definition |
|---|---|
| IRTC | International Research and Training Center |
| IRTT | Initial Round Trip Time |
| IRV | Improved Recovery Vehicle |
| IS | Information Superiority |
| IS | Interface Specification |
| IS | International Security |
| IS | InterSwitch |
| IS3 | In-transit Security and Survivability System |
| ISA | Industry Standard Architecture |
| ISA | Instruction Set Architecture |
| ISA | Intelligence Support Activity |
| ISA | International Standardization Agreement |
| ISA | Inter-Service Agreement |
| ISA | Inter-service Support Agreement |
| ISAP | Individual System Automation Plan |
| ISAR | Inverse Synthetic Aperture Radar |
| ISB | Initial Staging Base |
| ISB | Intermediate Staging Base |
| ISC | Information Systems Center |
| ISC | Information Systems Command |