AUI may stand for:
- Ethernet's Attachment Unit Interface, a 15-pin D-connector
- The constructed language aUI (language)
- The National Rail code for Ardlui railway station, United Kingdom
- Associated Universities, Inc., the corporation that operates the National Radio Astronomy Observatory (NRAO)
- Amiga User International, a monthly magazine dedicated to the Amiga computer
- Al Akhawayn University, a university located in Ifrane, Morocco
aUI is a constructed language created by W. John Weilgart (1913–1981), a philologist and psychoanalyst originally from Vienna, Austria. He described it as "the language of space" and published a general work in 1975 and later textbook.
Weilgart's motivation for inventing the language was to create a form of communication based on what he proposed to be universal, basic elements of human thought and expression, and incorporated it into his psychotherapy work.