| Acronym | Meaning |
| J6 | Joint Information Technology Directorate (Command |
| J7 | Joint Operational Plans & Interoperability Directorate |
| J8 | Joint Force Structure |
| J9 | Joint Public Affairs Directorate (Civilian-Military Cooperation) |
| JA | Japan (FIPS 10-4 Country Code) |
| JA | Japanese Language (ISO 639-1 Code) |
| JAFT | Just A Field Test |
| JAG | Judge Advocate General (military Law) |
| JAL | Japan Airlines |
| JAM | Jamaica (ISO 3166 Trigram) |
| JAMA | Journal Of The American Medical Association |
| JANUS | Joint Academic Network Using Satellites (UK) - Joint Army Navy Uniform Simulation -Joint Army-Navy Staff - Just ANother Useless Simulation (Note: The U.S. Army Janus Simulation Is Not An Acronym) |
| JATO | Jet-Assisted Take-Off |
| JAV | Javanese Language (ISO 639-2 Code) |
| JB | Junior Branch |
| JBFSA | Joint Blue Force Situational Awareness |
| JCATS | Joint Conflict And Tactical Simulation (djay-catts) |
| JCDB | Joint Common Data Base |
| JCDS | Joint Chiefs Of The Defence Staff |
| JCIDS | Joint Capabilities Integration And Development System |
| JCIET | Joint Combat Identification Evaluation Team |
| JCL | Job Control Language |
| JCP | Java Community Process |
| JCPM | Java Child Process Manager - Jesus Christ Prison Ministry |
| JCS | Joint Chiefs Of Staff |
| JD | Jack Daniels (whiskey) - Julian Day - Juris Doctor (Latin |
| JDAM | Joint Direct Attack Munition (djay-dam) |
| JDBC | Java Data Base Connectivity |
| JDCC | UK Joint Doctrine And Concepts Centre |
| JDEM | Joint Dark Energy Mission |
| JDK | Java Development Kit |
| JDL | Jewish Defense League |
| JE | Jersey (FIPS 10-4 Territory Code) |
| JEB | James Ewell Brown Stuart - Jeb Bush - Jeb Stuart - John Ellis Bush |
| JEE | Java Platform |
| JEFX | Joint Expeditionary Force EXperiment |
| JET | Joint European Torus |
| JEZ | Joint Engagement Zone |
| JFACC | Joint Force Air Component Commander |
| JFACTSU | U.S. Joint Forward Air Control Training And Standards Unit |
| JFC | Joint Force Commander |
| JFCOM | U.S. Joint Forces Command (jiff-comm) |
| JFET | Junction Field-Effect Transistor (jay-fett) |
| JFHQ | NCR -Joint Force Headquarters National Capital Region |
| JFK | John Fitzgerald Kennedy Or The Airport Named After Him. |
| JFLCC | Joint Force Land Component Commander |
| JFMCC | Joint Force Maritime Component Commander |
| JFO | Journal Of Field Ornithology |
| JFSOCC | Joint Force Special Operations Component Commander |
| JFTX | Joint Field Training Exercise |