USI
- Distinctive Software
- USI Tech
- USI Wireless
- Union Solidarity International
- Union of Independent Trade Unions (Portugal)
- Union of Students in Ireland
- Unione Sindacale Italiana
- Unique Student Identifier
- Unique Transaction Identifier
- United States of Indonesia
- Universal Stylus Initiative
- University of Siegen
- University of Southern Indiana
- Università della Svizzera italiana
- User System Interaction
- Usi (food)
- Usi County
- Usı
- Uši