U
- UA – Unauthorized Absence
- UAS – Unmanned Aerial System
- UAV – Unmanned Aerial Vehicle
- UCAV – Unmanned Combat Air Vehicle
- ULLS – Unit Level Logisitics System (U.S. Army)
- UMA – Unit Mobilization Assistor
- UN – United Nations
- US – Unserviceable
- USSS – United States Secret Service
- USAF – United States Air Force
- USAFE – United States Air Forces in Europe
- USA PATRIOT Act – Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act
- USAREC – US Army REcruiting Command
- USAREUR – US Army European Command
- USMC – United States Marine Corps
- USN – United States Navy
- USO – United Service Organizations (U.S. Military)
- USR – Unit Status Report
- UUV – Unmanned Underwater Vehicle
- UXB – Unexploded Bomb (bomb disposal; British)
- UXO – Unexploded Ordnance
Read more about this topic: List Of U.S. Government And Military Acronyms