UO
UO is an abbreviation for:
- Hong Kong Express Airways , Chinese airline (IATA code)
- Russian Federation according to the ICAO code
- Ultima Online , an online role-playing game
- Reverse osmosis , a method of obtaining ion-free water
- University of Oklahoma , the university in the US state of Oklahoma
- University of Oregon , the university in the US state of Oregon
- University of Ottawa , the university of the Canadian capital Ottawa
- Okres Ústí nad Orlicí , German: Wild Sword, expiring license plate
