- UO2 (uranium dioxide (nuclear))
- UO3 (uranium trioxide (nuclear))
- UO4 (uranyl peroxide (nuclear))
- UOA (United Ostomy Association)
- UOAI (United Ostomy Association, Inc.)
- UOB (Unit Order Of Battle)
- UOC (Ultrafast Optical Clock)
- UOD (Universe Of Discourse)
- UOE (University Outreach and Extension)
- UOES (User Operational Evaluation System)
- UOF (Universal Orbit Format)
- UOFA (University OF Alberta, Edmonton, Alberta, Canada)
- UOFC (University OF Calgary, Calgary, Alberta, Canada)
- UOFI (University of Illinois)
- U OF K (University of Khartoum)
- UofK (University of Khartoum (Sudan))
- UOFM (University of Michigan)
- UofO (University of Ottawa)
- UOFR (University Of Regina)
- UOFS (University of the Orange Free State)
- UofT (University of Toronto)
- UofW (University OF Waterloo, Waterloo, Ontario, Canada)
- UOG (Utility Optimization Group)
- UOH (Unity Of Honor)