ESI

ESI, Esi, or esi may refer to:

Chemistry

• Electrospray ionization, a technique used for mass spectrometry

Companies and organizations

• Electro Scientific Industries (ESI; Nasdaq: ESIO), a high-technology company based in Oregon, United States
• Employees’ State Insurance scheme, the national health and disability insurance for industry workers and other employees in India
• Erwin Schrödinger Institute for Mathematical Physics, an Austrian research institute
• ESI International, formerly Educational Services Institute, a workforce training firm based in Virginia, United States
• European Software Institute, a non-profit foundation launched as an initiative of the European Commission
• European Stability Initiative, a non-profit research and policy institute
• Express Scripts Incorporated, a pharmacy benefit manager
• Ernst Strüngmann Institute, a German research institute

Computer science

• Edge Side Includes, a markup language for edge level dynamic web content assembly
• Electronically Stored Information
• Enclosure Services Interface, a computer protocol used in SCSI enclosures
• ESI register, Extended Source Index register in the x86 microprocessor architecture
• Enterprise Southbridge Interface, Intel's interface used between the northbridge and southbridge, on server motherboards

Emergency medicine

• Emergency Severity Index, a triage algorithm for the hospital emergency department

People

• Esi Tonga (born 1988), a rugby league player

Others

• "esi" is the ISO 639-3 code for the North Alaskan Inupiat language
• Earth Similarity Index
• Electromagnetic source imaging
• Environmental Seismic Intensity scale
• Environmental Sustainability Index
• Epidural Steroid Injection
• Escadron spécial d'intervention, Belgium's former counter-terrorism force, now the Federal Police Special Units
• Espinosa, Minas Gerais, Brazil airport IATA code
• Ethical Sensory Introvert, in socionics
• Export substitution industrialization (ESI), sometimes called Export-Oriented Industrialisation (EOI), an economic trade policy