USI or Usi may stand for:

Organizations[edit]

• USI Tech, a suspected ponzi scheme
• USI Wireless, a Minnesota internet service provider
• Union of Independent Trade Unions (Portugal)
• Union of Students in Ireland, the representative body for students' unions in Ireland
• Unione Sindacale Italiana, an Italian trade union
• Union Solidarity International (USi), an international labour organising support organisation
• Unlimited Software Inc., see Distinctive Software

Places[edit]

• Usı, Tatarstan, a place in Russia
• Usi County, a county in westernmost Chagang province, North Korea
• United States of Indonesia, a state in Southeast Asia from 1949 to 1950
• University of Southern Indiana, a University located in Evansville, Indiana, United States
• University of Siegen, a University located in Siegen, North Rhine-Westphalia, Germany
• Università della Svizzera italiana, the University of Italian-speaking Switzerland

Other uses[edit]

• Usi (food), a starch dish of the Urhobo people of Nigeria
• Uši, an album by Czech band Uz jsme doma
• User System Interaction, a postgraduate engineering design program in the Netherlands
• Unique Student Identifier, a unique identifier for all students in Australia
• Unique Swap Identifier, see Unique Transaction Identifier, identifier for trades mandated by financial markets regulation
• Universal Stylus Initiative for interoperable active pen styluses for touchscreen devices
• USI: Under Special Investigation, 2010 TV series