UI or Ui can refer to:An alternate symbol for the international unit (IU)Eurocypria Airlines, IATA airline designatorUnemployment InsuranceUnit Intervals (Serial Data Communication)United IrelandUniversal indicatorUniversities IrelandUnix InternationalUser interfaceUi , a digraph used in some writing systemsUi, an ancient Phoenician colony located at the site of modern-day Tripoli in LibyaA